Finding the Zeros of a Parabola

🏆Practice zeros of a fuction

Finding the zeros of a quadratic function of the form \(y=ax^2+bx+c\)

Zero points of a function are its intersection points with the XX-axis.
To find them, we set Y=0 Y=0 ,
we get an equation that can sometimes be solved using a trinomial or the quadratic formula.

When trying to find the zero point, you can encounter three possible results:

  1. Two results -
    In this case, the function intersects the XX-axis at two different points.
  2. One result -
    In this case, the function intersects the XX-axis at only one point, meaning the vertex of the parabola is exactly on the XX-axis.
  3. No results -
    In this case, the function does not intersect the XX-axis at all, meaning it hovers above or below it.
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Test yourself on zeros of a fuction!

The following function has been graphed below:

\( f(x)=-x^2+5x+6 \)

Calculate points A and B.

BBBAAACCC

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Zero points describe a situation where the function equals zero.

Let's look at an example:
We have the function
X2−4x+5X^2-4x+5
We substitute into the quadratic formula and get:

−4±(−4)2−4∗1∗521=−4±−42 {-4 \pm \sqrt{(-4)^2-4*1*5} \over 21}=-\frac{4\pm\sqrt{-4}}{2}

This equation has no solution because the delta inside the root is negative. Therefore, this equation never equals zero, it hovers above the X-axis, and it has no zero points.

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Examples with solutions for Zeros of a Fuction

Exercise #1

The following function has been graphed below:

f(x)=−x2+5x+6 f(x)=-x^2+5x+6

Calculate points A and B.

BBBAAACCC

Video Solution

Step-by-Step Solution

To solve for the x-intercepts of the function f(x)=−x2+5x+6 f(x) = -x^2 + 5x + 6 , we will find the roots of the quadratic equation −x2+5x+6=0 -x^2 + 5x + 6 = 0 .

Let's attempt to factor this quadratic equation first. Rewrite the equation as follows:

−x2+5x+6=0 -x^2 + 5x + 6 = 0 .

To factor, we look for two numbers that multiply to −6-6 (the product of aa and cc, where a=−1a = -1 and c=6c = 6) and add to 55 (the middle coefficient bb).

The numbers that satisfy this condition are −1-1 and 66.

Thus, the quadratic can be factored as:

(x−6)(x+1)=0(x - 6)(x + 1) = 0.

Setting each factor equal to zero gives us:

x−6=0x - 6 = 0 or x+1=0x + 1 = 0.

Solving these equations, we find:

x=6x = 6 and x=−1x = -1.

Thus, the points A and B, the x-intercepts of the function, are:

(−1,0)(-1, 0) and (6,0) (6, 0).

Therefore, the solution to the problem is (−1,0),(6,0)(-1, 0), (6, 0).

Answer

(−1,0),(6,0) (-1,0),(6,0)

Exercise #2

The following function has been graphed below:

f(x)=x2−6x+8 f(x)=x^2-6x+8

Calculate points A and B.

AAABBB

Video Solution

Step-by-Step Solution

To solve the problem of finding points A and B on the graph of the function f(x)=x2−6x+8 f(x) = x^2 - 6x + 8 , we need to determine where this quadratic function equals zero.

Step-by-step Approach:

  • Step 1: Check Factoring Possibility
    The quadratic function is given by:
f(x)=x2−6x+8 f(x) = x^2 - 6x + 8

We will attempt to factor this quadratic expression. We are looking for two numbers that multiply to the constant term, 8, and add to the coefficient of x x , which is −6-6.

  • Step 2: Identify Factors
    The numbers 4 4 and 2 2 multiply to 8 8 and add to −6-6, if we consider their negative counterparts, −4-4 and −2-2:
(x−4)(x−2)=x2−6x+8 (x - 4)(x - 2) = x^2 - 6x + 8

This matches our expression, confirming that it is the correct factorization.

  • Step 3: Solve for Roots
    Set each factor equal to zero:
x−4=0⇒x=4 x - 4 = 0 \quad \Rightarrow \quad x = 4 x−2=0⇒x=2 x - 2 = 0 \quad \Rightarrow \quad x = 2

Thus, the points where the function intersects the x-axis, which are the roots, are (2,0) (2,0) and (4,0) (4,0) .

Therefore, the solution to the problem is that points A and B are at (2,0)(2,0) and (4,0)(4,0).

Final Solution:
The points A and B are (2,0)(2,0) and (4,0)(4,0).

Answer

(2,0),(4,0) (2,0),(4,0)

Exercise #3

The following function has been graphed below:

f(x)=x2−8x+16 f(x)=x^2-8x+16

Calculate point A.

AAACCC

Video Solution

Step-by-Step Solution

Let's solve the problem by following the outlined analysis:

  • Step 1: Identify important points on the parabola.
  • Step 2: Calculate the y-intercept by evaluating f(0) f(0) .
  • Step 3: Confirm understanding of the vertex form and its characteristics.

Step 1: Identify the significant points on the function.
The function given is f(x)=x2−8x+16 f(x) = x^2 - 8x + 16 .

This function can be seen as
f(x)=(x−4)2 f(x) = (x - 4)^2 .

This format not only indicates it is always non-negative but also reveals the vertex is located at x=4 x = 4 , importantly, with f(x)=0 f(x) = 0 .

Step 2: Calculate the y-intercept.
Evaluate the function at x=0 x = 0 :

f(0)=02−8⋅0+16=16 f(0) = 0^2 - 8 \cdot 0 + 16 = 16 .
So, the y-intercept is (0,16) (0, 16) .

Thus, point A, which is often labeled at a crucial intercept, corresponds to the y-intercept of the function. The calculation confirms that point A is (0,16) (0, 16) .

Therefore, the solution to the problem is (0,16) (0,16) .

Answer

(0,16) (0,16)

Exercise #4

The following function has been graphed below:

f(x)=x2−6x+5 f(x)=x^2-6x+5

Calculate points A and B.

AAABBB

Video Solution

Step-by-Step Solution

To solve for the points A and B, we need to find the roots of the function f(x)=x2−6x+5 f(x) = x^2 - 6x + 5 where f(x)=0 f(x) = 0 .

Let's proceed step-by-step:

  • Step 1: Set the function to zero
    We begin by setting the equation to zero: x2−6x+5=0 x^2 - 6x + 5 = 0 .
  • Step 2: Factor the quadratic
    We need to factor the expression. We look for two numbers that multiply to c=5 c = 5 and add to b=−6 b = -6 . These numbers are −1-1 and −5-5.
  • Step 3: Write the factorization
    Therefore, we can write the quadratic as: (x−1)(x−5)=0(x - 1)(x - 5) = 0.
  • Step 4: Solve for the roots
    Set each factor equal to zero: \begin{align*} x - 1 &= 0 \\ x &= 1 \end{align*} \begin{align*} x - 5 &= 0 \\ x &= 5 \end{align*} The roots are x=1 x = 1 and x=5 x = 5 .
  • Step 5: Identify the Points A and B
    The points A and B, where the function intersects the x-axis, are (1,0)(1, 0) and (5,0)(5, 0).

Thus, the coordinates of points A and B are (1,0),(5,0) (1,0),(5,0) , which matches choice 1.

Answer

(1,0),(5,0) (1,0),(5,0)

Exercise #5

The following function has been plotted on the graph below:

f(x)=x2−8x+16 f(x)=x^2-8x+16

Calculate point C.

CCC

Video Solution

Step-by-Step Solution

To solve the exercise, first note that point C lies on the X-axis.

Therefore, to find it, we need to understand what is the X value when Y equals 0.

Let's set the equation equal to 0:

0=xÂČ-8x+16

We'll use the preferred method (trinomial or quadratic formula) to find the X values, and we'll discover that

X=4

Answer

(4,0) (4,0)

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