Find Point C on f(x)=x²-8x+16: Quadratic Function Graph Analysis

Quadratic Functions with X-intercept Identification

The following function has been plotted on the graph below:

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

Calculate point C.

CCC

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find the coordinates of point C
00:06 At point C Y=0, the point is on the X-axis
00:10 Substitute Y=0 in the function and solve for X
00:19 We want to factor the function into a trinomial
00:23 This is the appropriate factorization
00:30 Isolate X
00:35 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

The following function has been plotted on the graph below:

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

Calculate point C.

CCC

2

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

3

Final Answer

(4,0) (4,0)

Key Points to Remember

Essential concepts to master this topic
  • X-intercept Rule: Set y = 0 to find where graph crosses x-axis
  • Factoring Method: x28x+16=(x4)2=0 x^2-8x+16 = (x-4)^2 = 0 gives x = 4
  • Verification: Check that f(4) = 16 - 32 + 16 = 0 ✓

Common Mistakes

Avoid these frequent errors
  • Confusing x-intercept with y-intercept
    Don't substitute x = 0 to find point C on the x-axis = wrong coordinate (0,16)! Point C is where the parabola crosses the x-axis, not the y-axis. Always set f(x) = 0 to find x-intercepts.

Practice Quiz

Test your knowledge with interactive questions

The following function has been graphed below:

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

Calculate points A and B.

BBBAAACCC

FAQ

Everything you need to know about this question

How do I know point C is on the x-axis?

+

Looking at the graph, point C is clearly marked on the horizontal line where y = 0. Any point on the x-axis has a y-coordinate of 0.

Why does this quadratic have only one x-intercept?

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The function f(x)=x28x+16 f(x) = x^2 - 8x + 16 is a perfect square trinomial: (x4)2 (x-4)^2 . This means the parabola just touches the x-axis at x = 4, creating a double root.

What if I can't factor the quadratic easily?

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You can always use the quadratic formula: x=b±b24ac2a x = \frac{-b \pm \sqrt{b^2-4ac}}{2a} . For this problem: x=8±64642=4 x = \frac{8 \pm \sqrt{64-64}}{2} = 4

How do I write the final answer as a coordinate?

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Since point C is at x = 4 on the x-axis, the y-coordinate is 0. Write it as an ordered pair: (4, 0) where x comes first, then y.

Could there be other points like C on this parabola?

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No! A quadratic function can have at most 2 x-intercepts. This perfect square has exactly one x-intercept at x = 4, making point C unique.

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