The Vertex of the Parabola: Finding a stationary point

Examples with solutions for The Vertex of the Parabola: Finding a stationary point

Exercise #1

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 #2

The following function has been graphed below:

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

Calculate point C.

CCCAAABBB

Video Solution

Step-by-Step Solution

To solve this problem, we'll calculate the vertex of the parabola given by the quadratic function f(x)=x26x f(x) = x^2 - 6x .

  • Step 1: Identify the coefficients a=1 a = 1 and b=6 b = -6 .
  • Step 2: Use the vertex formula x=b2a x = -\frac{b}{2a} to find the x-coordinate of the vertex.
  • Step 3: Substitute the calculated x-coordinate back into the function to find the y-coordinate.

Now, let's compute:

Step 1: The function is f(x)=x26x f(x) = x^2 - 6x with coefficients a=1 a = 1 and b=6 b = -6 .

Step 2: Apply the vertex formula: x=62×1=62=3 x = -\frac{-6}{2 \times 1} = \frac{6}{2} = 3 .

Step 3: For x=3 x = 3 , substitute into f(x) f(x) to find the y-coordinate:

f(3)=(3)26×3=918=9 f(3) = (3)^2 - 6 \times 3 = 9 - 18 = -9 .

Therefore, the coordinates of the point C, which is the vertex, are (3,9)(3, -9).

The correct answer is (3,9)(3, -9), which corresponds to the given correct choice.

Answer

(3,9) (3,-9)

Exercise #3

The following function has been graphed below.

f(x)=x26x+8 f(x)=x^2-6x+8

Calculate point B.

BBB

Video Solution

Step-by-Step Solution

To calculate point B, we should determine the vertex of the quadratic function f(x)=x26x+8 f(x) = x^2 - 6x + 8 .

The x-coordinate of the vertex can be found using the formula x=b2a x = -\frac{b}{2a} .

In our equation, we have a=1 a = 1 and b=6 b = -6 , therefore:

x=62×1=62=3 x = -\frac{-6}{2 \times 1} = \frac{6}{2} = 3

Next, we substitute x=3 x = 3 back into the function to find the y-coordinate:

f(3)=326×3+8=918+8=1 f(3) = 3^2 - 6 \times 3 + 8 = 9 - 18 + 8 = -1

Thus, the vertex, which is point B, is (3,1) (3, -1) .

Therefore, the solution indicates that point B is at (3,1) (3, -1) .

Answer

(3,1) (3,-1)

Exercise #4

The following function has been graphed below:

f(x)=x2+5x+6 f(x)=-x^2+5x+6

Calculate point C.

BBBAAACCC

Video Solution

Step-by-Step Solution

To answer the question, we must first remember the formula for finding the vertex of a parabola:

Now let's substitute the known data into the formula:

-5/2(-1)=-5/-2=2.5

In other words, the x-coordinate of the vertex of the parabola is found when the X value equals 2.5.

Now let's substitute this into the parabola equation to find the Y value:

-(2.5)²+5*2.5+6= 12.25

Therefore, the coordinates of the vertex of the parabola are (2.5, 12.25).

Answer

(212,1214) (2\frac{1}{2},12\frac{1}{4})