Examples with solutions for Parabola of the Form y=(x-p)²+k: Identify the positive and negative domain

Exercise #1

Find the negative area of the function

y=(x+3)24 y=-(x+3)^2-4

Video Solution

Step-by-Step Solution

The function given is y=(x+3)24 y = -(x+3)^2 - 4 . This function represents a parabola opening downwards, with the vertex at (3,4) (-3, -4) . Because y=(x+3)24 y = -(x+3)^2 - 4 is a downward-opening parabola with a vertex below the x-axis at -4, it means every point on the parabola has a y-value less than zero. Thus, for all values of x x , the function is negative.

The entire graph of this quadratic function lies below the x-axis; therefore, any form of "area" discussed here would necessarily be negative since the function never crosses into positive y-values (it is not asking for the integration under the curve relative to x-axis as such).

Consequently, the situation describes that the parabola completely lies under the x-axis across its domain: for all real x x .

Therefore, the solution to the problem is: For all x x , the area is negative.

Answer

For all X

Exercise #2

Find the negative area of the function

y=(x1)24 y=(x-1)^2-4

Video Solution

Step-by-Step Solution

To solve this problem, we'll consider the steps as follows:

  • Step 1: Recognize the given function as a standard parabola centered at (h,k)=(1,4) (h, k) = (1, -4) that opens upwards.
  • Step 2: The formula y=(x1)24 y = (x-1)^2 - 4 represents the parabola with vertex at (1,4) (1, -4) .
  • Step 3: Determine roots by solving the equation (x1)24=0(x-1)^2 - 4 = 0.
  • Step 4: Rearrange to (x1)2=4(x-1)^2 = 4 leading to x1=±2x - 1 = \pm 2.
  • Step 5: Solve these to find roots: x=3x = 3 and x=1x = -1.
  • Step 6: Calculate regions where the function is negative by testing intervals between the roots.

Now, we apply these steps:

Step 1: The function, expressed in its vertex form, indicates a parabola opening upwards (since the coefficient of (x1)2(x-1)^2 is positive).

Step 2: The equation for determining where the parabola touches the x-axis is (x1)24=0(x−1)^2−4=0. Solving this, we rearrange it to (x1)2=4(x-1)^2 = 4.

Step 3: Solving for (x1)2=4(x-1)^2 = 4, gives x1=2x - 1 = 2 or x1=2x - 1 = -2, leading to solutions x=3x = 3 and x=1x = -1.

Step 4: The parabola is negative between these roots. So, the inequality (x1)2<4(x-1)^2 < 4 holds true for 1<x<3 -1 < x < 3 .

Therefore, the negative area of the function lies in the interval 1<x<3 -1 < x < 3 .

Conclusively, the negative domain of the function is 1<x<3 -1 < x < 3 .

Answer

-1 < x < 3

Exercise #3

Find the positive area of the function

y=(x4)2+1 y=(x-4)^2+1

Video Solution

Step-by-Step Solution

To solve this problem, we will analyze the given quadratic function:

The function is y=(x4)2+1 y = (x-4)^2 + 1 .

Step 1: Identify the vertex of the parabola.
The function y=(x4)2+1 y = (x-4)^2 + 1 is in the form y=(xh)2+k y = (x-h)^2 + k , where h=4 h = 4 and k=1 k = 1 . This gives the vertex at the point (4,1) (4, 1) .

Step 2: Analyze the shape and direction of the parabola.
This parabola opens upwards because the coefficient of (x4)2 (x-4)^2 is positive. Hence, the vertex is the minimum point of the parabola.

Step 3: Determine when the function is positive.
Since the minimum value of the function at the vertex is 1 1 , and all quadratic functions in the form of (xh)2+k (x-h)^2 + k are non-negative, this means the function y=(x4)2+1 y = (x-4)^2 + 1 is always positive for any real number x x .

Step 4: Comparison with the choices:
From the explanation, the function is always positive for all x x . Thus, the correct choice is: For all X.

The positive area of the function covers all real numbers x x .

Therefore, the function is positive for all x x .

Answer

For all X

Exercise #4

Find the positive area of the function

y=(x+5)24 y=(x+5)^2-4

Video Solution

Step-by-Step Solution

To find the positive area of the function y=(x+5)24 y = (x+5)^2-4 , follow these steps:

  • Step 1: Identify when the function is greater than zero.
    We need (x+5)24>0 (x+5)^2 - 4 > 0 .
  • Step 2: Find the roots of (x+5)24=0 (x+5)^2 - 4 = 0 .
    Solving, we set: (x+5)2=4 (x+5)^2 = 4 .
  • Step 3: Solve for (x+5)2=4 (x+5)^2 = 4 .
    Take the square root on both sides: x+5=±2 x + 5 = \pm 2 .
    This gives: x+5=2 x + 5 = 2 or x+5=2 x + 5 = -2 .
    Thus, x=3 x = -3 or x=7 x = -7 .
  • Step 4: Identify intervals.
    We need to look at intervals determined by the roots: (,7) (-\infty, -7) , (7,3) (-7, -3) , and (3,) (-3, \infty) .
  • Step 5: Determine where the function is positive by testing each interval:
    - For x<7 x < -7 , choose x=8 x = -8 , then ((8)+5)24=94=5 ((-8)+5)^2 - 4 = 9 - 4 = 5 (positive).
    - For 7<x<3 -7 < x < -3 , choose x=5 x = -5 , then ((5)+5)24=04=4 ((-5)+5)^2 - 4 = 0 - 4 = -4 (negative).
    - For x>3 x > -3 , choose x=0 x = 0 , then (5)24=254=21 (5)^2 - 4 = 25 - 4 = 21 (positive).

Therefore, the positive area of the function is for x<7 x < -7 and 3<x -3 < x .

Answer

x < -7 , -3 < x

Exercise #5

Find the positive area of the function

y=(x6)2+4 y=(x-6)^2+4

Video Solution

Step-by-Step Solution

We begin by analyzing the given function y=(x6)2+4 y = (x-6)^2 + 4 . This is a parabola in vertex form, with the vertex at the point (6,4) (6, 4) . The expression (x6)2 (x-6)^2 represents the square of (x6) (x-6) , and as a square, it can only be zero or positive, thus (x6)20(x-6)^2 \geq 0.

Adding 4, the smallest value that y y can take is therefore 4 4 , which occurs when (x6)2=0(x-6)^2 = 0. That means at the vertex, the function achieves its minimum value of y=4 y = 4 , which is clearly positive.

This implies the function y=(x6)2+4 y = (x-6)^2 + 4 is never negative for any real value of x x . Hence, the area above the x-axis is positive or non-negative for all values of x x , which means no restrictions on the domain are necessary based on positivity.

Thus, the solution concludes that the function remains non-negative for all x x , satisfying the condition of positive area.

Therefore, the correct choice is For all X.

Answer

For all X

Exercise #6

Find the negative area of the function

y=(x4)2+9 y=-(x-4)^2+9

Video Solution

Step-by-Step Solution

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

  • Step 1: Set up the inequality (x4)2+9<0 -(x-4)^2 + 9 < 0 .
  • Step 2: Simplify to get (x4)2>9 (x-4)^2 > 9 .
  • Step 3: Solve (x4)2>9 (x-4)^2 > 9 into two linear inequalities.
  • Step 4: Identify the solution intervals.

Let's work through these steps:

Step 1: Set up the inequality:
We have (x4)2+9<0 -(x-4)^2 + 9 < 0 .

Step 2: Simplify the inequality:
This becomes (x4)2>9 (x-4)^2 > 9 .

Step 3: Solve the quadratic inequality:
The inequality (x4)2>9 (x-4)^2 > 9 can be split into two cases:
x4>3 x-4 > 3 or x4<3 x-4 < -3 .

Simplifying these gives:
x>7 x > 7 or x<1 x < 1 .

Step 4: Identify the solution intervals:
Thus, the intervals where the function is negative are x<1 x < 1 or x>7 x > 7 .

Therefore, the correct solution is the interval x<1,7<x x < 1 , 7 < x .

This matches choice 3.

Answer

x < 1 , 7 < x

Exercise #7

Find the negative area of the function

y=(x+3)236 y=(x+3)^2-36

Video Solution

Step-by-Step Solution

To solve this problem, follow these steps:

  • Step 1: Express the function in a more workable form.
  • Step 2: Solve for the points where the function equals zero.
  • Step 3: Determine where the function is negative within the identified intervals.

Let's begin:

Step 1: The given function is y=(x+3)236 y = (x+3)^2 - 36 . This can be rewritten as a difference of squares:

y=((x+3)6)((x+3)+6)=(x3)(x+9) y = \left((x+3) - 6\right)\left((x+3) + 6\right) = (x-3)(x+9) .

Step 2: Set the function equal to zero to find the roots:

(x3)(x+9)=0 (x-3)(x+9) = 0 .

The roots are x=3 x = 3 and x=9 x = -9 .

Step 3: Test the sign of the quadratic in each interval determined by the roots:

- For x<9 x < -9 , choose x=10 x = -10 : (x3)(x+9)(x-3)(x+9) becomes negative, because ()()(-)(-) = positive.

- For 9<x<3 -9 < x < 3 , choose x=0 x = 0 : (x3)(x+9)(x-3)(x+9) becomes negative because ()(+)(-)(+) = negative.

- For x>3 x > 3 , choose x=10 x = 10 : (x3)(x+9)(x-3)(x+9) becomes positive because (+)(+)(+)(+) = positive.

Therefore, the function is negative within the interval 9<x<3 -9 < x < 3 .

Therefore, the correct answer is 9<x<3 -9 < x < 3 .

Answer

-9 < x < 3

Exercise #8

Find the positive area of the function

y=(x+3)2+25 y=-(x+3)^2+25

Video Solution

Step-by-Step Solution

To solve this problem, follow these steps:

  • Step 1: Find the x-intercepts by solving the equation (x+3)2+25=0 -(x+3)^2 + 25 = 0 .
  • Step 2: Determine when the expression (x+3)2+25 -(x+3)^2 + 25 is positive.
  • Step 3: Verify the correct answer choice based on the solution.

Now let's work through each step:

Step 1: Solve (x+3)2+25=0 -(x+3)^2 + 25 = 0 .

Rewriting, we have:

(x+3)2=25 -(x+3)^2 = -25

(x+3)2=25(x+3)^2 = 25

This gives x+3=±5 x+3 = \pm 5 .

Solving these, we find x=2 x = 2 and x=8 x = -8 .

Step 2: Determine when (x+3)2+25>0 -(x+3)^2 + 25 > 0 .

We know that the parabola is downward opening, so it will be positive between the roots found, 8 -8 and 2 2 .

Thus, the positive interval is 8<x<2 -8 < x < 2 .

Step 3: Verify the correct answer choice.

The correct answer, matching the solution above, is choice 1: 8<x<2 -8 < x < 2 .

Therefore, the positive area of the function occurs in the interval 8<x<2 -8 < x < 2 .

Answer

-8 < x < 2

Exercise #9

Find the positive area of the function

y=(x4)2+1 y=-(x-4)^2+1

Video Solution

Step-by-Step Solution

To solve this problem, follow these steps:

  • Step 1: Identify the vertex form of the parabola, which is given as y=(x4)2+1 y = -(x-4)^2 + 1 .
  • Step 2: Convert the equation to find the x-intercepts (roots), set y=0 y = 0 :

We set the equation equal to zero:

(x4)2+1=0 -(x-4)^2 + 1 = 0

(x4)2=1 -(x-4)^2 = -1

(x4)2=1 (x-4)^2 = 1

  • Step 3: Solve for x x by taking the square root of both sides:

x4=±1 x-4 = \pm 1

This gives two solutions for x x :

x=4+1=5 x = 4 + 1 = 5

x=41=3 x = 4 - 1 = 3

  • Step 4: Determine the interval where y y is positive by analyzing intervals around the roots 3 and 5.
  • Check intervals: x<3 x < 3 , 3<x<5 3 < x < 5 , and x>5 x > 5 .
  • Since the vertex (highest point) occurs at x=4 x = 4 , we know the parabola is positive between its roots from 3 to 5.

Thus, the segment of the domain where the parabola lies above the x-axis is:

3<x<5 3 < x < 5

The correct choice is: 3<x<5 3 < x < 5 .

Answer

3 < x < 5