Examples with solutions for Product Representation: With fractions

Exercise #1

Find the positive and negative domains of the following function:

y=(x12)(x+612) y=\left(x-\frac{1}{2}\right)\left(x+6\frac{1}{2}\right)

Determine for which values of x x the following is true:

f(x) < 0

Step-by-Step Solution

Let us solve the problem step by step to find: x x values for which f(x) < 0 .

Firstly, identify the roots of the function y=(x12)(x+612) y = \left(x - \frac{1}{2}\right)\left(x + 6\frac{1}{2}\right) :

  • The root from (x12)=0 \left(x - \frac{1}{2}\right) = 0 is x=12 x = \frac{1}{2} .
  • The root from (x+612)=0 \left(x + 6\frac{1}{2}\right) = 0 is x=612 x = -6\frac{1}{2} .

These roots divide the real number line into three intervals:

  • x<612 x < -6\frac{1}{2}
  • 612<x<12 -6\frac{1}{2} < x < \frac{1}{2}
  • x>12 x > \frac{1}{2}

To determine where the function is negative, evaluate the sign in each interval:

  • For x<612 x < -6\frac{1}{2} : Both factors (x12) (x - \frac{1}{2}) and (x+612) (x + 6\frac{1}{2}) are negative, so their product is positive.
  • For 612<x<12 -6\frac{1}{2} < x < \frac{1}{2} : (x12) (x - \frac{1}{2}) is negative and (x+612) (x + 6\frac{1}{2}) is positive, thus the product is negative.
  • For x>12 x > \frac{1}{2} : Both factors are positive, so their product is positive.

Hence, the function is negative on the interval: 612<x<12 -6\frac{1}{2} < x < \frac{1}{2} .

Answer

-6\frac{1}{2} < x < \frac{1}{2}

Exercise #2

Look at the function below:

y=(2x214)2 y=-\left(2x-2\frac{1}{4}\right)^2

Then determine for which values of x x the following is true:

f(x) < 0

Step-by-Step Solution

The function is given in vertex form: y=(2x214)2 y = -\left(2x - 2\frac{1}{4}\right)^2 , which translates to y=(2x2.25)2 y = -\left(2x - 2.25\right)^2 . The vertex occurs when the expression inside the square is zero, which is at x=118 x = 1\frac{1}{8} . This is the maximum point due to the negative coefficient, making the function value at the vertex equal to zero.

For f(x)<0 f(x) < 0 , the square term (2x2.25)2 \left(2x - 2.25\right)^2 must be non-zero. Thus, set 2x214=0 2x - 2\frac{1}{4} = 0 to find the x x that needs to be excluded:

2x2.25=0 2x - 2.25 = 0

2x=2.25 2x = 2.25

x=1.125 x = 1.125 or x=118 x = 1\frac{1}{8}

Therefore, for f(x)<0 f(x) < 0 , x x should not be equal to 118 1\frac{1}{8} .

The correct condition is: x118 x \neq 1\frac{1}{8} .

Answer

x118 x\ne1\frac{1}{8}

Exercise #3

Find the positive and negative domains of the following function:

y=(13x+16)(x415) y=\left(\frac{1}{3}x+\frac{1}{6}\right)\left(-x-4\frac{1}{5}\right)

Then determine for which values of x x the following is true:

f(x) < 0

Step-by-Step Solution

The function y=(13x+16)(x415) y = \left(\frac{1}{3}x + \frac{1}{6}\right)\left(-x - 4\frac{1}{5}\right) requires us to analyze the sign of the product for various x x values.

First, we must find the zeros of each factor:

  • The zero of 13x+16 \frac{1}{3}x + \frac{1}{6} is found by solving 13x+16=0 \frac{1}{3}x + \frac{1}{6} = 0 :
    Subtract 16 \frac{1}{6} to get:
    13x=16 \frac{1}{3}x = -\frac{1}{6}
    Multiply both sides by 3:
    x=12 x = -\frac{1}{2} .
  • The zero of x415 -x - 4\frac{1}{5} is found by solving x415=0 -x - 4\frac{1}{5} = 0 :
    Add 415 4\frac{1}{5} to get:
    x=415 -x = 4\frac{1}{5}
    Multiply by 1-1 to find:
    x=415 x = -4\frac{1}{5} .

Next, we identify the intervals defined by these zeros: x<415 x < -4\frac{1}{5} , 415<x<12 -4\frac{1}{5} < x < -\frac{1}{2} , and x>12 x > -\frac{1}{2} .

We will determine the sign of the function in each interval:

  • In x<415 x < -4\frac{1}{5} :
    - 13x+16 \frac{1}{3}x + \frac{1}{6} and x415 -x - 4\frac{1}{5} are both negative (since both points are below their respective roots), resulting in a positive product.
  • In 415<x<12 -4\frac{1}{5} < x < -\frac{1}{2} :
    - 13x+16 \frac{1}{3}x + \frac{1}{6} is negative and x415 -x - 4\frac{1}{5} is positive, resulting in a negative product.
  • In x>12 x > -\frac{1}{2} :
    - 13x+16 \frac{1}{3}x + \frac{1}{6} and x415 -x - 4\frac{1}{5} are both positive, resulting in a positive product.

The function is negative in the interval 415<x<12 -4\frac{1}{5} < x < -\frac{1}{2} . Thus, the correct answer corresponding to where the function is negative is the complementary intervals x>12 x > -\frac{1}{2} or x<415 x < -4\frac{1}{5} , which matches choice 2.

Therefore, the solution is x>12 x > -\frac{1}{2} or x<415 x < -4\frac{1}{5} .

Answer

x > -\frac{1}{2} or x < -4\frac{1}{5}

Exercise #4

Look at the function below:

y=(3x+30)2 y=\left(3x+30\right)^2

Then determine for which values of x x the following is true:

f(x) > 0

Step-by-Step Solution

To determine the values of x x for which the function y=(3x+30)2 y = (3x + 30)^2 is greater than zero, consider the following steps:

  • Step 1: Recognize the structure of the function. The function is of the form (expression)2 (\text{expression})^2 . For the function to be greater than zero, the expression inside the square must not equal zero.
  • Step 2: Solve 3x+30=0 3x + 30 = 0 to find when the function equals zero.
    Subtract 30 from both sides: 3x=30 3x = -30 .
    Divide by 3: x=10 x = -10 .
  • Step 3: Exclude x=10 x = -10 from the domain where the function is greater than 0. For all x10 x \neq -10 , (3x+30)2 (3x + 30)^2 is positive because it results from squaring a non-zero real number.

Therefore, f(x)>0 f(x) > 0 for all x10 x \neq -10 .

The correct answer is x10 x\ne-10 .

Answer

x10 x\ne-10

Exercise #5

Look at the function below:

y=(2x16)2 y=\left(2x-16\right)^2

Then determine for which values of x x the following is true:

f(x) > 0

Step-by-Step Solution

To determine when the function y=(2x16)2 y = (2x - 16)^2 is greater than zero, we observe the following:

  • The function's expression, (2x16)2(2x - 16)^2, is a square and thus always non-negative (0 \geq 0 ).
  • The expression will equate to zero when the inside term is zero: 2x16=02x - 16 = 0.
  • Solve the equation 2x16=02x - 16 = 0 to find x=8x = 8.
  • Therefore, (2x16)2=0(2x - 16)^2 = 0 only at x=8x = 8.
  • For y>0 y > 0 , (2x16)2(2x - 16)^2 must be greater than zero, which occurs for all x x except x=8 x = 8.

The solution is x8 x \ne 8 , which means y y is positive for all x x except x=8 x = 8 .

Answer

x8 x\ne8

Exercise #6

Look at the function below:

y=(x4.4)(x2.3) y=\left(x-4.4\right)\left(x-2.3\right)

Then determine for which values of x x the following is true:

f(x) < 0

Step-by-Step Solution

To determine when the quadratic function y=(x4.4)(x2.3) y = (x - 4.4)(x - 2.3) is negative, we need to analyze the sign of the product across the different intervals defined by its roots.

  • Step 1: Identify the roots of the function. The roots occur when each factor equals zero, which are x=2.3 x = 2.3 and x=4.4 x = 4.4 .
  • Step 2: Divide the x-axis into intervals based on these roots: x<2.3 x < 2.3 , 2.3<x<4.4 2.3 < x < 4.4 , and x>4.4 x > 4.4 .
  • Step 3: Test a value from each interval:
    • For x<2.3 x < 2.3 , try x=2 x = 2 : y=(24.4)(22.3)=(2.4)(0.3)=0.72 y = (2 - 4.4)(2 - 2.3) = (-2.4)(-0.3) = 0.72 , so the product is positive.
    • For 2.3<x<4.4 2.3 < x < 4.4 , try x=3 x = 3 : y=(34.4)(32.3)=(1.4)(0.7)=0.98 y = (3 - 4.4)(3 - 2.3) = (-1.4)(0.7) = -0.98 , so the product is negative.
    • For x>4.4 x > 4.4 , try x=5 x = 5 : y=(54.4)(52.3)=(0.6)(2.7)=1.62 y = (5 - 4.4)(5 - 2.3) = (0.6)(2.7) = 1.62 , so the product is positive.

From this analysis, we see that the quadratic function is negative for values of x x in the interval 2.3<x<4.4 2.3 < x < 4.4 . This is the range where the function changes sign from positive to negative back to positive.

Therefore, the correct answer is 2.3<x<4.4 2.3 < x < 4.4 .

Answer

2.3 < x < 4.4

Exercise #7

Find the positive and negative domains of the following function:

y=(13x16)(x415) y=\left(\frac{1}{3}x-\frac{1}{6}\right)\left(-x-4\frac{1}{5}\right)

Determine for which values of x x the following is true:

f\left(x\right) > 0

Step-by-Step Solution

To find the set of x x values where y=(13x16)(x415) y = \left(\frac{1}{3}x-\frac{1}{6}\right)\left(-x-4\frac{1}{5}\right) is positive, we need to determine where each factor changes sign.

First, find the zeros of the linear factors:

  • For 13x16=0\frac{1}{3}x - \frac{1}{6} = 0:
    Solving gives 13x=16 \frac{1}{3}x = \frac{1}{6} or x=12 x = \frac{1}{2} .
  • For x415=0-x - 4\frac{1}{5} = 0:
    Solving gives x=415-x = -4\frac{1}{5} or x=415 x = -4\frac{1}{5} .

These zeros split the real number line into three intervals. Let's determine the sign of each expression in the intervals:

  • Interval (,415)(-\infty, -4\frac{1}{5}):
    - 13x16<0\frac{1}{3}x-\frac{1}{6} < 0 and x415>0-x-4\frac{1}{5} > 0
  • Interval (415,12)(-4\frac{1}{5}, \frac{1}{2}):
    - 13x16<0\frac{1}{3}x-\frac{1}{6} < 0 and x415<0-x-4\frac{1}{5} < 0
  • Interval (12,)(\frac{1}{2}, \infty):
    - 13x16>0\frac{1}{3}x-\frac{1}{6} > 0 and x415<0-x-4\frac{1}{5} < 0

The product (13x16)(x415)\left(\frac{1}{3}x-\frac{1}{6}\right)\left(-x-4\frac{1}{5}\right) is positive in the interval where both factors are negative or both are positive:

Therefore, the solution is 415<x<12-4\frac{1}{5} < x < -\frac{1}{2}, matching with choice 3.

Answer

-4\frac{1}{5} < x < -\frac{1}{2}

Exercise #8

Find the positive and negative domains of the function:

y=(x12)(x+612) y=\left(x-\frac{1}{2}\right)\left(x+6\frac{1}{2}\right)

Determine for which values of x x the following is true:

f\left(x\right) > 0

Step-by-Step Solution

To find when the function y=(x12)(x+612) y = \left(x - \frac{1}{2}\right)\left(x + 6\frac{1}{2}\right) is positive, we proceed as follows:

First, identify the roots of the expression by solving x12=0 x - \frac{1}{2} = 0 and x+612=0 x + 6\frac{1}{2} = 0 . These calculations give us the roots x=12 x = \frac{1}{2} and x=612 x = -6\frac{1}{2} , or x=132 x = -\frac{13}{2} .

Next, determine the sign of the product (x12)(x+132) (x - \frac{1}{2})(x + \frac{13}{2}) over the intervals defined by these roots:

  • Interval 1: x<132 x < -\frac{13}{2} . In this region, both x12 x - \frac{1}{2} and x+132 x + \frac{13}{2} are negative, so their product is positive.
  • Interval 2: 132<x<12 -\frac{13}{2} < x < \frac{1}{2} . In this region, x+132 x + \frac{13}{2} is positive and x12 x - \frac{1}{2} is negative, so their product is negative.
  • Interval 3: x>12 x > \frac{1}{2} . In this region, both x12 x - \frac{1}{2} and x+132 x + \frac{13}{2} are positive, so their product is positive.

Therefore, the function is positive for x<612 x < -6\frac{1}{2} and x>12 x > \frac{1}{2} .

Thus, the solution is:
x>12 x > \frac{1}{2} or x<612 x < -6\frac{1}{2}

Answer

x > \frac{1}{2} or x < -6\frac{1}{2}

Exercise #9

Look at the function below:

y=(5x1)2 y=\left(5x-1\right)^2

Then determine for which values of x x the following is true:

f(x) < 0

Step-by-Step Solution

To find where f(x)=(5x1)2<0 f(x) = (5x - 1)^2 < 0 , we start by recognizing a fundamental property of squares:

  • The square of any real number is always non-negative. Therefore, (5x1)20(5x - 1)^2 \geq 0 for all real x x .

This implies that (5x1)2(5x - 1)^2 can never be less than zero for any real value of x x .

The inequality (5x1)2<0 (5x - 1)^2 < 0 has no solution in the real numbers.

Therefore, there are no values of x x for which f(x)<0 f(x) < 0 is true.

So the logical conclusion is: True for no values of x x .

Answer

True for no values of x x

Exercise #10

Look at the function below:

y=(5x1)(4x14) y=\left(5x-1\right)\left(4x-\frac{1}{4}\right)

Then determine for which values of x x the following is true:

f(x) < 0

Step-by-Step Solution

To solve the problem of determining for which values of x x the function y=(5x1)(4x14) y = (5x-1)(4x-\frac{1}{4}) is negative, we will follow these steps:

  • Step 1: Determine the roots of the function by setting each factor equal to zero.
  • Step 2: Analyze the sign of the function on intervals defined by these roots.
  • Step 3: Identify where the function is negative based on this analysis.

Let's proceed with these steps:

Step 1: Find the roots of the function.

To find the roots, set each factor equal to zero:

5x1=0x=15 5x - 1 = 0 \Rightarrow x = \frac{1}{5}

4x14=0x=116 4x - \frac{1}{4} = 0 \Rightarrow x = \frac{1}{16}

Step 2: Determine the intervals on the number line.

The roots divide the number line into the following intervals: (,116) (-\infty, \frac{1}{16}) , (116,15) (\frac{1}{16}, \frac{1}{5}) , and (15,) (\frac{1}{5}, \infty) .

Step 3: Analyze the sign of the function in each interval:

  • For x<116 x < \frac{1}{16} : Both 5x1 5x - 1 and 4x14 4x - \frac{1}{4} are negative. Hence, their product is positive.
  • For 116<x<15 \frac{1}{16} < x < \frac{1}{5} : Here, 5x1 5x - 1 is negative, and 4x14 4x - \frac{1}{4} is positive, making the product negative.
  • For x>15 x > \frac{1}{5} : Both 5x1 5x - 1 and 4x14 4x - \frac{1}{4} are positive, resulting in a positive product.

Now, consolidate the findings:

The function y=(5x1)(4x14) y = (5x-1)(4x-\frac{1}{4}) is less than zero for values 116<x<15 \frac{1}{16} < x < \frac{1}{5} .

Therefore, the solution to the given problem is 116<x<15 \frac{1}{16} < x < \frac{1}{5} .

Answer

\frac{1}{16} < x < \frac{1}{5}

Exercise #11

Look at the function below:

y=(13x+15)2 y=-\left(\frac{1}{3}x+15\right)^2

Then determine for which values of x x the following is true:

f(x) > 0

Step-by-Step Solution

To solve the problem, we must analyze the given function y=(13x+15)2 y = -\left(\frac{1}{3}x + 15\right)^2 .

Firstly, as a general rule of algebra, the square of any real number is non-negative. Therefore, (13x+15)20\left(\frac{1}{3}x + 15\right)^2 \geq 0 for all real values of x x .

Secondly, the function is y=(13x+15)2 y = -\left(\frac{1}{3}x + 15\right)^2 . The negative sign in front affects the entire expression, making the range of y y non-positive (y0 y \leq 0 ) since the expression within the square is always non-negative. This implies every y y is either zero or negative.

Thus, the function y y will never be greater than zero because multiplying any non-negative number by (1)(-1) results in a non-positive number.

Conclusion: The function f(x)>0 f(x) > 0 is true for no values of x x .

Therefore, the correct answer choice is: True for no values of x x .

Answer

True for no values of x x

Exercise #12

Look at the function below:

y=(13x+15)2 y=-\left(\frac{1}{3}x+15\right)^2

Then determine for which values of x x the following is true:

f(x) < 0

Step-by-Step Solution

To solve this problem, let's examine the function y=(13x+15)2 y = -\left(\frac{1}{3}x + 15\right)^2 and determine when y<0 y < 0 .

Step 1: Analyze the expression inside the function.
The function involves the square of a linear term, (13x+15)\left(\frac{1}{3}x + 15\right). The square of any real number is always non-negative, meaning (13x+15)20\left(\frac{1}{3}x + 15\right)^2 \geq 0.

Step 2: Consider the effect of multiplying by 1-1.
When this non-negative square is multiplied by 1-1, the result is always non-positive: (13x+15)20 -\left(\frac{1}{3}x + 15\right)^2 \leq 0.

Step 3: Identify when the function y y is less than zero.
For the function to be strictly less than zero, the squared term must be strictly greater than zero: (13x+15)2>0\left(\frac{1}{3}x + 15\right)^2 > 0.

Step 4: Determine the zero point to exclude it.
The expression (13x+15)2=0\left(\frac{1}{3}x + 15\right)^2 = 0 only when 13x+15=0\frac{1}{3}x + 15 = 0. Solving this equation gives:

  • 13x+15=0\frac{1}{3}x + 15 = 0
  • 13x=15\frac{1}{3}x = -15
  • x=45x = -45

This means that the function y=0 y = 0 at x=45 x = -45 . To satisfy y<0 y < 0 , x x must be any value other than 45-45.

Therefore, the condition for which the function value is negative is: x45 x \neq -45 .

Answer

x45 x\ne-45

Exercise #13

Look at the function below:

y=(2x+30)2 y=\left(2x+30\right)^2

Then determine for which values of x x the following is true:

f(x) < 0

Step-by-Step Solution

To solve this problem, we analyze the function y=(2x+30)2 y = (2x + 30)^2 .

Notice that this function involves a squared term, (2x+30) (2x + 30) , which is squared to yield the expression (2x+30)2 (2x + 30)^2 . A crucial property of squares is that the square of any real number is never negative. Thus, for any real number z z , z20 z^2 \geq 0 .

Since (2x+30)2 (2x + 30)^2 is the square of a real expression, it implies that this expression is always greater than or equal to zero. Therefore, it is impossible for y y to be less than zero. There are no real values of x x that would satisfy the inequality f(x)<0 f(x) < 0 .

Consequently, the correct interpretation is that the inequality (2x+30)2<0 (2x + 30)^2 < 0 holds true for no values of x x .

Therefore, the solution to the problem is:

True for no values of x x

Answer

True for no values of x x

Exercise #14

Given the function:

y=(2x214)2 y=-\left(2x-2\frac{1}{4}\right)^2

Determine for which values of X the following holds:

f(x) > 0

Step-by-Step Solution

To solve this problem, we begin by analyzing the function y=(2x214)2 y = -\left(2x - 2\frac{1}{4}\right)^2 .

The expression inside the square, 2x214 2x - 2\frac{1}{4} , can take any real value depending on x x . However, when squared (2x214)2 \left(2x - 2\frac{1}{4}\right)^2 , it becomes non-negative for all real x x , meaning it is always greater than or equal to zero.

Since y y is defined as the negative of this square—y=(2x214)2 y = -\left(2x - 2\frac{1}{4}\right)^2 —the function y y is always less than or equal to zero. In other words, y0 y \leq 0 for all real values of x x .

Therefore, there are no values of x x that make f(x)>0 f(x) > 0 , as the function outputs non-positive values exclusively.

Thus, the solution to the problem is No x.

Answer

No x

Exercise #15

Look at the following function:

y=(x12)(x+312) y=\left(x-\frac{1}{2}\right)\left(-x+3\frac{1}{2}\right)

Determine for which values of x x the following is true:

f(x) < 0

Step-by-Step Solution

To solve this problem, we'll begin by finding the roots of the quadratic equation y=(x12)(x+312) y = \left(x - \frac{1}{2}\right)\left(-x + 3\frac{1}{2}\right) .

First, set each factor equal to zero:

  • x12=0 x - \frac{1}{2} = 0 gives x=12 x = \frac{1}{2}
  • x+312=0-x + 3\frac{1}{2} = 0 gives x=312 x = 3\frac{1}{2}

This means the roots of the quadratic are x=12 x = \frac{1}{2} and x=312 x = 3\frac{1}{2} .

Next, analyze the intervals determined by these roots:

  • Interval 1: x<12 x < \frac{1}{2}
  • Interval 2: 12<x<312 \frac{1}{2} < x < 3\frac{1}{2}
  • Interval 3: x>312 x > 3\frac{1}{2}

Perform a sign test within these intervals:

  • For x<12 x < \frac{1}{2} : Both x12 x - \frac{1}{2} and x+312 -x + 3\frac{1}{2} are negative, thus their product is positive (negative times negative is positive).
  • For 12<x<312 \frac{1}{2} < x < 3\frac{1}{2} : The factor x12 x - \frac{1}{2} is positive and x+312-x + 3\frac{1}{2} is positive as well, thus product is positive (positive times positive is positive).
  • For x>312 x > 3\frac{1}{2} : x12 x - \frac{1}{2} is positive, but x+312-x + 3\frac{1}{2} is negative, so the product is negative (positive times negative is negative).

Therefore, the quadratic function is negative for: x>312 x > 3\frac{1}{2} and x<12 x < \frac{1}{2} .

The solution to the problem is: x>312 x > 3\frac{1}{2} or x<12 x < \frac{1}{2} .

Answer

x > 3\frac{1}{2} or x < \frac{1}{2}

Exercise #16

Find the positive and negative domains of the function below:

y=(x12)(x+312) y=\left(x-\frac{1}{2}\right)\left(-x+3\frac{1}{2}\right)

Determine for which values of x x the following is true:

f(x) > 0

Step-by-Step Solution

To solve this problem, we'll determine when the product (x12)(x+312) (x - \frac{1}{2})(-x + 3\frac{1}{2}) is positive. This involves finding the roots of the equation and testing the intervals between these roots:

Step 1: **Determine the roots of the factors.**
- The first factor x12=0 x - \frac{1}{2} = 0 gives the root x=12 x = \frac{1}{2} .
- The second factor x+312=0 -x + 3\frac{1}{2} = 0 gives the root x=312 x = 3\frac{1}{2} .

Step 2: **Identify intervals based on these roots.**
- The roots divide the x x -axis into three intervals: x<12 x < \frac{1}{2} , 12<x<312 \frac{1}{2} < x < 3\frac{1}{2} , and x>312 x > 3\frac{1}{2} .

Step 3: **Analyze the sign of the function in each interval.**
- For x<12 x < \frac{1}{2} :
- x12<0 x - \frac{1}{2} < 0 and x+312>0 -x + 3\frac{1}{2} > 0 , so the product is negative.
- For 12<x<312 \frac{1}{2} < x < 3\frac{1}{2} :
- Both x12>0 x - \frac{1}{2} > 0 and x+312>0 -x + 3\frac{1}{2} > 0 , so the product is positive.
- For x>312 x > 3\frac{1}{2} :
- x12>0 x - \frac{1}{2} > 0 and x+312<0 -x + 3\frac{1}{2} < 0 , so the product is negative.

Therefore, the intervals where y>0 y > 0 are 12<x<312 \frac{1}{2} < x < 3\frac{1}{2} .

This matches the given correct answer choice: 12<x<312 \frac{1}{2} < x < 3\frac{1}{2} .

Answer

\frac{1}{2} < x < 3\frac{1}{2}

Exercise #17

Look at the function below:

y=(4x+22)2 y=\left(4x+22\right)^2

Then determine for which values of x x the following is true:

f(x) < 0

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Analyze the given function.
  • Step 2: Determine the nature of (4x+22)2 (4x + 22)^2 .
  • Step 3: Conclude whether it can ever be negative.

Step 1: We are given the function y=(4x+22)2 y = (4x + 22)^2 . This is a quadratic function expressed as a square of a linear term.

Step 2: Consider the expression (4x+22) (4x + 22) . Whatever value this linear expression takes, its square, (4x+22)2 (4x + 22)^2 , will always be non-negative. This is because the square of a real number is never negative.

Step 3: To find when (4x+22)2<0 (4x + 22)^2 < 0 , we realize that since squares are non-negative, they cannot actually be negative. Thus, (4x+22)20 (4x + 22)^2 \geq 0 for all values of x x , and can never be less than zero.

Therefore, no value of x x will make f(x)<0 f(x) < 0 .

The conclusion is that there is no value of x x for which f(x)<0 f(x) < 0 .

Answer

No value of x x

Exercise #18

Find the positive and negative domains of the function:

y=(x13)(x214) y=\left(x-\frac{1}{3}\right)\left(-x-2\frac{1}{4}\right)

Determine for which values of x x the following is true:

f(x) > 0

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Identify the roots of the quadratic expression.
  • Step 2: Determine the sign of each factor in intervals defined by these roots.
  • Step 3: Identify where the product of these factors is positive.

Now, let's work through each step:

Step 1: Identify the roots.
The given function is y=(x13)(x214) y = \left(x - \frac{1}{3}\right)\left(-x - 2\frac{1}{4}\right) . To find the roots, solve each factor for zero:

  • x13=0 x - \frac{1}{3} = 0 gives x=13 x = \frac{1}{3} .
  • x214=0-x - 2\frac{1}{4} = 0 gives x=214 x = -2\frac{1}{4} .

Step 2: Determine the sign of each factor in the intervals defined by these roots.
The zeros divide the x-axis into three intervals: (,214)(-∞, -2\frac{1}{4}), (214,13)(-2\frac{1}{4}, \frac{1}{3}), and (13,)(\frac{1}{3}, ∞).

Step 3: Test the signs and find where the product is positive.

  • For x<214 x < -2\frac{1}{4} , test with x=3 x = -3 : - x13=313<0 x - \frac{1}{3} = -3 - \frac{1}{3} < 0 - x214=3214>0-x - 2\frac{1}{4} = 3 - 2\frac{1}{4} > 0 - Product: Negative
  • For 214<x<13 -2\frac{1}{4} < x < \frac{1}{3} , test with x=0 x = 0 : - x13=013<0 x - \frac{1}{3} = 0 - \frac{1}{3} < 0 - x214=0214>0-x - 2\frac{1}{4} = 0 - 2\frac{1}{4} > 0 - Product: Positive
  • For x>13 x > \frac{1}{3} , test with x=1 x = 1 : - x13=113>0 x - \frac{1}{3} = 1 - \frac{1}{3} > 0 - x214=1214<0-x - 2\frac{1}{4} = -1 - 2\frac{1}{4} < 0 - Product: Negative

Therefore, the solution to f(x)>0 f(x) > 0 is in the interval:

214<x<13 -2\frac{1}{4} < x < \frac{1}{3} .

Answer

-2\frac{1}{4} < x < \frac{1}{3}

Exercise #19

Find the positive and negative domains of the following function:

y=(2x12)(x214) y=\left(2x-\frac{1}{2}\right)\left(x-2\frac{1}{4}\right)

Determine for which values of x x the following is true:

f(x) < 0

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Identify the roots of the quadratic function.
  • Step 2: Analyze the intervals between these roots to determine where the function is negative.
  • Step 3: Write the final solution as the interval where f(x)<0 f(x) < 0 .

Now, let's work through each step:
Step 1: Determine the roots by solving each factor for zero:
- 2x12=02x=12x=14 2x - \frac{1}{2} = 0 \Rightarrow 2x = \frac{1}{2} \Rightarrow x = \frac{1}{4} .
- x214=0x=214 x - 2\frac{1}{4} = 0 \Rightarrow x = 2\frac{1}{4} .
Thus, the roots are x=14 x = \frac{1}{4} and x=214 x = 2\frac{1}{4} .

Step 2: Analyze the intervals determined by the roots x=14 x = \frac{1}{4} and x=214 x = 2\frac{1}{4} :

  • Interval 1: x<14 x < \frac{1}{4}
  • Interval 2: 14<x<214 \frac{1}{4} < x < 2\frac{1}{4}
  • Interval 3: x>214 x > 2\frac{1}{4}

Step 3: Test each interval:

  • For interval 1 x<14 x < \frac{1}{4} : Choose x=0 x = 0 . f(0)=(2(0)12)(0214)=(12)(214)=98>0 f(0) = \left(2(0) - \frac{1}{2}\right)(0 - 2\frac{1}{4}) = \left(-\frac{1}{2}\right) \left(-2\frac{1}{4}\right) = \frac{9}{8} > 0 .
  • For interval 2 14<x<214 \frac{1}{4} < x < 2\frac{1}{4} : Choose x=1 x = 1 . f(1)=(2(1)12)(1214)=(32)(54)=158<0 f(1) = \left(2(1) - \frac{1}{2}\right)(1 - 2\frac{1}{4}) = \left(\frac{3}{2}\right)(-\frac{5}{4}) = -\frac{15}{8} < 0 .
  • For interval 3 x>214 x > 2\frac{1}{4} : Choose x=3 x = 3 . f(3)=(2(3)12)(3214)=(112)(34)=338>0 f(3) = \left(2(3) - \frac{1}{2}\right)(3 - 2\frac{1}{4}) = \left(\frac{11}{2}\right)\left(\frac{3}{4}\right) = \frac{33}{8} > 0 .

Therefore, the solution to f(x)<0 f(x) < 0 is found in the interval 14<x<214 \frac{1}{4} < x < 2\frac{1}{4} .

Answer

\frac{1}{4} < x < 2\frac{1}{4}

Exercise #20

Look at the function below:

y=(5x1)2 y=\left(5x-1\right)^2

Then determine for which values of x x the following is true:

f(x) > 0

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Recognize that any square of a real number is greater than zero unless the number itself is zero.
  • Step 2: Find when the expression 5x1 5x - 1 equals zero, since the square is zero only at this point.
  • Step 3: Exclude this value to determine when the quadratic is strictly greater than zero.

Let's work through each step:
Step 1: The expression given is y=(5x1)2 y = (5x - 1)^2 . We know that the square of any non-zero real number is positive.
Step 2: Set the inner expression to zero to find the critical point:
5x1=0 5x - 1 = 0
Solving for x x , we add 1 to both sides:
5x=1 5x = 1
Divide both sides by 5:
x=15 x = \frac{1}{5}
Step 3: Therefore, (5x1)2>0 (5x - 1)^2 > 0 for all x15 x \neq \frac{1}{5} .
This means that the quadratic expression is greater than zero for all real values of x x except x=15 x = \frac{1}{5} .

Thus, the solution to the problem is x15 x\ne\frac{1}{5} .

Answer

x15 x\ne\frac{1}{5}