Solve (x+3)²-9: Finding X-Axis Intersections of a Shifted Parabola

Quadratic Functions with X-intercept Analysis

Find the intersection of the function

y=(x+3)29 y=(x+3)^2-9

With the X

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find the intersection point with the X-axis
00:03 Substitute Y=0 and solve to find the intersection point
00:10 We want to isolate X
00:18 Extract the root
00:25 When extracting a root there are 2 solutions, positive and negative
00:33 Solve each possibility to find the intersection point
00:54 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

Find the intersection of the function

y=(x+3)29 y=(x+3)^2-9

With the X

2

Step-by-step solution

To solve the problem of finding the intersection of the function y=(x+3)29 y = (x + 3)^2 - 9 with the x-axis, we need to set y=0 y = 0 because the x-axis is defined by y=0 y = 0 .

Starting with the equation:

(x+3)29=0(x + 3)^2 - 9 = 0

Our goal is to solve for x x . Let's simplify the equation:

Add 9 to both sides:

(x+3)2=9(x + 3)^2 = 9

Next, take the square root of both sides:

x+3=±3x + 3 = \pm 3

This gives us two equations to solve:

  • x+3=3x + 3 = 3
  • x+3=3x + 3 = -3

Solving these equations, we find:

For x+3=3x + 3 = 3:

x=0x = 0

For x+3=3x + 3 = -3:

x=6x = -6

Thus, the x-intercepts are (0,0)(0, 0) and (6,0)(-6, 0). These are the points where the graph intersects the x-axis.

The correct answer, matching the choices given, is choice 3: (0,0),(6,0)(0, 0), (-6, 0).

3

Final Answer

(0,0),(6,0) (0,0),(-6,0)

Key Points to Remember

Essential concepts to master this topic
  • X-Intercepts: Set y = 0 and solve the resulting quadratic equation
  • Technique: (x+3)2=9 (x+3)^2 = 9 becomes x+3=±3 x+3 = ±3
  • Check: Substitute x = 0 and x = -6: both give y = 0 ✓

Common Mistakes

Avoid these frequent errors
  • Finding y-intercepts instead of x-intercepts
    Don't set x = 0 to find x-intercepts = gives you (0, -9) which is wrong! This finds where the graph crosses the y-axis, not the x-axis. Always set y = 0 to find x-intercepts.

Practice Quiz

Test your knowledge with interactive questions

Which equation represents the function:

\( y=x^2 \)

moved 2 spaces to the right

and 5 spaces upwards.

FAQ

Everything you need to know about this question

Why do I set y = 0 to find x-intercepts?

+

The x-axis is defined by y = 0. To find where a graph crosses the x-axis, you need to find all points where the y-coordinate equals zero!

What does the ± symbol mean when I take the square root?

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When you take the square root of both sides, you get two possible values: positive and negative. For 9=±3 \sqrt{9} = ±3 , this means both +3 and -3.

How do I know which form of the answer to choose?

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Look carefully at the answer choices! X-intercepts are always written as (x-value, 0) since they're points on the x-axis where y = 0.

Can I expand the equation instead of using the vertex form?

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Yes! You could expand (x+3)29 (x+3)^2-9 to get x2+6x x^2+6x , then factor. But working with the vertex form is usually faster and cleaner.

What if I get decimal or fraction answers?

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That's perfectly normal! Many parabolas have x-intercepts that aren't whole numbers. Just make sure to simplify and check your work by substitution.

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