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.

Suggested Topics to Practice in Advance

  1. The quadratic function
  2. Parabola
  3. Plotting the Quadratic Function Using Parameters a, b and c

Practice Zeros of a Fuction

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:

(x6)(x+1)=0(x - 6)(x + 1) = 0.

Setting each factor equal to zero gives us:

x6=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)=x26x+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)=x26x+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: x26x+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: (x1)(x5)=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 #3

The following function has been graphed below:

f(x)=x28x+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)=x28x+16 f(x) = x^2 - 8x + 16 .

This function can be seen as
f(x)=(x4)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)=0280+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 plotted on the graph below:

f(x)=x28x+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=x²-8x+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)

Exercise #5

The following function has been graphed below:

f(x)=x23x4 f(x)=x^2-3x-4

Calculate points A and B.

CCCAAABBB

Video Solution

Step-by-Step Solution

To solve for points A and B, we find the x-intercepts of the function by setting:

f(x)=x23x4=0 f(x) = x^2 - 3x - 4 = 0

We check if it can be factored:

Factor x23x4 x^2 - 3x - 4 . The factors of -4 that add to -3 are -4 and 1.

Thus, factor the function as (x4)(x+1)=0 (x - 4)(x + 1) = 0 .

Set each factor to zero:

  • x4=0 x - 4 = 0 implies x=4 x = 4
  • x+1=0 x + 1 = 0 implies x=1 x = -1

These are the x-intercepts, or roots, of the quadratic function.

Therefore, the coordinates of points A and B, where the function intersects the x-axis, are A(1,0) A(-1, 0) and B(4,0) B(4, 0) .

The correct choice corresponding to these points is option 3: A(1,0),B(4,0) A(-1,0), B(4,0) .

Thus, the solution to the problem is A(1,0),B(4,0) A(-1,0), B(4,0) .

Answer

A(1,0),B(4,0) A(-1,0),B(4,0)

Exercise #6

The following function has been graphed below:

f(x)=x26x f(x)=x^2-6x

Calculate points A and B.

AAABBB

Video Solution

Step-by-Step Solution

To solve for the points A and B, where the graph of f(x)=x26x f(x) = x^2 - 6x intersects the x-axis, let's solve the equation f(x)=0 f(x) = 0 :
1. Write the equation in standard form:
x26x=0 x^2 - 6x = 0 .

2. Factor the quadratic equation:
x(x6)=0 x(x - 6) = 0 .

3. Set each factor equal to zero:
x=0 x = 0 or x6=0 x - 6 = 0 .

4. Solve each equation for x x :
x=0 x = 0 and x=6 x = 6 .

Thus, the points where the function intersects the x-axis, also the points A and B, are (0,0) (0,0) and (6,0) (6,0) .

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

Answer

(6,0),(0,0) (6,0),\lparen0,0)

Exercise #7

The following function has been graphed below:

f(x)=x26x+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)=x26x+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)=x26x+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:
(x4)(x2)=x26x+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:
x4=0x=4 x - 4 = 0 \quad \Rightarrow \quad x = 4 x2=0x=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 #8

Determine the points of intersection of the function

y=(x3)(x+3) y=(x-3)(x+3)

With the X

Video Solution

Step-by-Step Solution

To determine the points of intersection of the function y=(x3)(x+3) y=(x-3)(x+3) with the x-axis, we need to set y y to zero and solve for x x .

Follow these steps:

  • Step 1: Set the function equal to zero: (x3)(x+3)=0 (x-3)(x+3) = 0 .
  • Step 2: Apply the zero-product property, solving each factor for zero:
    • For x3=0 x-3=0 :
    • x=3 x = 3
    • For x+3=0 x+3=0 :
    • x=3 x = -3

Thus, the points of intersection of the function with the x-axis, or the x-intercepts, are (3,0)(-3, 0) and (3,0)(3, 0).

Therefore, the solution to the problem, confirming x-intercepts, is (3,0),(3,0)(-3, 0), (3, 0).

Answer

(3,0),(3,0) (-3,0),(3,0)

Exercise #9

Determine the points of intersection of the function

y=(x5)(x+5) y=(x-5)(x+5)

With the X

Video Solution

Step-by-Step Solution

In order to find the point of the intersection with the X-axis, we first need to establish that Y=0.

 

0 = (x-5)(x+5)

When we have an equation of this type, we know that one of these parentheses must be equal to 0, so we begin by checking the possible options.

x-5 = 0
x = 5

 

x+5 = 0
x = -5

That is, we have two points of intersection with the x-axis, when we discover their x points, and the y point is already known to us (0, as we placed it):

(5,0)(-5,0)

This is the solution!

Answer

(5,0),(5,0) (5,0),(-5,0)

Exercise #10

Determine the points of intersection of the function

y=x(x+5) y=x(x+5)

With the X

Video Solution

Step-by-Step Solution

To determine the points of intersection with the x-axis for the function y=x(x+5) y = x(x+5) , follow these steps:

  • Step 1: Set the function equal to zero to find the x-intercepts: y=0 y = 0 .
  • Step 2: Solve the equation x(x+5)=0 x(x+5) = 0 .

Considering the product x(x+5)=0 x(x+5) = 0 :

  • If x=0 x = 0 , then one solution is x=0 x = 0 .
  • If x+5=0 x+5 = 0 , then solving for x x gives x=5 x = -5 .

Thus, the two points of intersection with the x-axis are:

(5,0)(-5, 0) and (0,0)(0, 0).

Therefore, the points of intersection of the function y=x(x+5) y = x(x+5) with the x-axis are (5,0)(-5, 0) and (0,0)(0, 0).

Answer

(5,0),(0,0) (-5,0),(0,0)

Exercise #11

Determine the points of intersection of the function

y=(x+7)(x+2) y=(x+7)(x+2)

With the X

Video Solution

Step-by-Step Solution

To find the points of intersection, follow these steps:

  • Step 1: The function given is y=(x+7)(x+2) y = (x+7)(x+2) . We are interested in where this function intersects the x-axis, which occurs when y=0 y = 0 .
  • Step 2: Set the function equal to zero: (x+7)(x+2)=0 (x+7)(x+2) = 0 .
  • Step 3: Solve for x x using the zero-product property, which states that if the product of two factors is zero, then at least one of the factors must be zero.

Now, solve the equation:
Step 1: Set x+7=0 x+7 = 0 , which gives x=7 x = -7 .
Step 2: Set x+2=0 x+2 = 0 , which gives x=2 x = -2 .

These values are the x x -coordinates where the function intersects the x-axis. Since the y-coordinates at each of these points is zero, the intersection points are (7,0) (-7,0) and (2,0) (-2,0) .

Therefore, the points of intersection are (2,0)(-2,0) and (7,0)(-7,0).

Answer

(2,0),(7,0) (-2,0),(-7,0)

Exercise #12

Determine the points of intersection of the function

y=(x+3)(x3) y=(x+3)(x-3)

With the X

Video Solution

Step-by-Step Solution

To determine the points of intersection of the function y=(x+3)(x3) y = (x+3)(x-3) with the x-axis, we need to find the x-values where y=0 y = 0 . These are called the x-intercepts.

We begin by setting the function equal to zero:

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

Using the zero-product property, if a product of two terms is zero, then at least one of the factors must be zero. Thus, we set each factor equal to zero and solve for x x :

  • First factor: x+3=0 x + 3 = 0
    • Solving for x x , we subtract 3 from both sides:
      x=3 x = -3
  • Second factor: x3=0 x - 3 = 0
    • Solving for x x , we add 3 to both sides:
      x=3 x = 3

Hence, the solutions for x x where y=0 y = 0 are x=3 x = -3 and x=3 x = 3 .

Therefore, the points of intersection of the function with the x-axis are (3,0) (-3, 0) and (3,0) (3, 0) .

Comparing with the given answer choices, the correct choice is (3,0),(3,0) (3,0),(-3,0) .

Therefore, the points of intersection are (3,0),(3,0) (3,0),(-3,0) .

Answer

(3,0),(3,0) (3,0),(-3,0)

Exercise #13

Determine the points of intersection of the function

y=(x11)(x+1) y=(x-11)(x+1)

With the X

Video Solution

Step-by-Step Solution

To determine the points where the function intersects the x-axis, we need to find the x-intercepts. These occur where y=0 y = 0 .

The function is given as y=(x11)(x+1) y = (x-11)(x+1) . To find the x-intercepts, we set this function equal to zero:

(x11)(x+1)=0 (x-11)(x+1) = 0 .

This equation implies that the product is zero when either x11=0 x-11 = 0 or x+1=0 x+1 = 0 .

Solving these equations, we find:

  • x11=0 x-11 = 0 leads to x=11 x = 11 .
  • x+1=0 x+1 = 0 leads to x=1 x = -1 .

Thus, the points of intersection with the x-axis are (1,0)(-1, 0) and (11,0)(11, 0).

Therefore, the solution to the problem is (1,0),(11,0)(-1, 0), (11, 0).

Answer

(1,0),(11,0) (-1,0),(11,0)

Exercise #14

Determine the points of intersection of the function

y=(x+8)(x9) y=(x+8)(x-9)

With the X

Video Solution

Step-by-Step Solution

The solution to the problem involves finding the x-intercepts of the given quadratic function, which are the points where the function intersects the x-axis (i.e., where y=0 y = 0 ).

Step by step solution:

  • Set the function equal to zero: (x+8)(x9)=0 (x+8)(x-9) = 0 .
  • The product of two terms is zero if and only if at least one of the terms is zero. Therefore, we solve:
    x+8=0 x+8 = 0 or x9=0 x-9 = 0 .
  • For x+8=0 x+8 = 0 :
    Subtract 8 from both sides to isolate x x :
    x=8 x = -8 .
  • For x9=0 x-9 = 0 :
    Add 9 to both sides to isolate x x :
    x=9 x = 9 .

The function intersects the x-axis at the points (8,0)(-8, 0) and (9,0)(9, 0).

Therefore, the points of intersection of the function with the x-axis are (8,0)(-8, 0) and (9,0)(9, 0).

Answer

(8,0),(9,0) (-8,0),(9,0)

Exercise #15

Determine the points of intersection of the function

y=(4x+8)(x+1) y=(4x+8)(x+1)

With the X

Video Solution

Step-by-Step Solution

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

  • Step 1: Set the function y=(4x+8)(x+1) y = (4x + 8)(x + 1) equal to zero, i.e., (4x+8)(x+1)=0 (4x + 8)(x + 1) = 0 .
  • Step 2: Apply the zero-product property to resulting factors.
  • Step 3: Solve each equation for x x .

Now, let's work through each step:
Step 1: We start by setting the equation to zero:
(4x+8)(x+1)=0(4x + 8)(x + 1) = 0.

Step 2: Using the zero-product property, we find:
1. 4x+8=04x + 8 = 0
2. x+1=0x + 1 = 0

Step 3: Solve each of these equations for x x :

For 4x+8=04x + 8 = 0, subtract 8 from both sides to get 4x=84x = -8. Divide both sides by 4, resulting in:
x=2x = -2.

For x+1=0x + 1 = 0, subtract 1 from both sides to get:
x=1x = -1.

Thus, the points of intersection of the function with the x-axis are the solutions we just found. At these points, the y-value is zero, giving us the intersection points as (1,0)(-1, 0) and (2,0)(-2, 0).

Therefore, the solution to the problem is (1,0),(2,0)(-1, 0), (-2, 0).

Answer

(1,0),(2,0) (-1,0),(-2,0)