Find the X-Axis Intersections of y = 2x(2x + 4)

Quadratic Functions with Zero-Product Property

Determine the points of intersection of the function

y=2x(2x+4) y=2x(2x+4)

With the X

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:09 Let's find where the graph crosses the X-axis.
00:12 Remember, at this point, the value of Y is zero.
00:16 So, we set Y equal to zero, and solve to find the X values. Let's figure it out!
00:23 Check what makes each part of the equation equal to zero.
00:27 Great! You've found one solution. Let's move on!
00:32 Now, let's isolate X in the next equation.
00:36 Awesome! This is your second solution.
00:40 And that's how we solve this problem. Great job!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Determine the points of intersection of the function

y=2x(2x+4) y=2x(2x+4)

With the X

2

Step-by-step solution

To determine the points of intersection of the function y=2x(2x+4) y = 2x(2x+4) with the x-axis, we must find where the function equals zero. Such points occur where y=0 y = 0 .

Start by setting the equation to zero:

2x(2x+4)=0 2x(2x + 4) = 0

Using the zero-product property, which states that if a product of multiple factors is zero, then at least one of the factors must be zero, we solve as follows:

  • Set each factor to zero: 2x=0 2x = 0 and 2x+4=0 2x + 4 = 0 .
  • Solving 2x=0 2x = 0 : Divide both sides by 2 to get x=0 x = 0 .
  • Solving 2x+4=0 2x + 4 = 0 : Subtract 4 from both sides to get 2x=4 2x = -4 , then divide by 2 to get x=2 x = -2 .

Thus, the x-intercepts are at x=0 x = 0 and x=2 x = -2 .

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

By comparing with the provided multiple-choice options, the correct answer is indeed choice 1: (2,0),(0,0) (-2,0),(0,0) .

3

Final Answer

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

Key Points to Remember

Essential concepts to master this topic
  • X-intercepts: Set the function equal to zero to find intersections
  • Zero-Product Property: If ab=0 ab = 0 , then a=0 a = 0 or b=0 b = 0
  • Verification: Check that y=0 y = 0 when x=0 x = 0 and x=2 x = -2

Common Mistakes

Avoid these frequent errors
  • Confusing x-intercepts with y-coordinates
    Don't think x-intercepts have non-zero y-values like (0,2) or (-2,-2)! X-intercepts always have y = 0 because they're on the x-axis. Always remember that x-intercepts are points where the graph crosses the x-axis, so they're in the form (x, 0).

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

Why do we set the function equal to zero to find x-intercepts?

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X-intercepts are points where the graph crosses the x-axis. On the x-axis, the y-coordinate is always zero, so we need y=0 y = 0 to find these crossing points!

What is the zero-product property and why can I use it here?

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The zero-product property says if a×b=0 a \times b = 0 , then either a=0 a = 0 or b=0 b = 0 (or both). Since 2x(2x+4)=0 2x(2x+4) = 0 is a product of two factors, we can set each factor to zero separately.

Do I need to expand the function first?

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No! Keep it factored as 2x(2x+4) 2x(2x+4) . The factored form makes it much easier to apply the zero-product property directly.

How do I know which points are the correct x-intercepts?

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X-intercepts are always in the form (x-value, 0). From our solutions x=0 x = 0 and x=2 x = -2 , the x-intercepts are (0,0) (0, 0) and (2,0) (-2, 0) .

Can I verify my answer by substituting back?

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Absolutely! Check: when x=0 x = 0 : y=2(0)(2(0)+4)=0 y = 2(0)(2(0)+4) = 0
When x=2 x = -2 : y=2(2)(2(2)+4)=(4)(0)=0 y = 2(-2)(2(-2)+4) = (-4)(0) = 0

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