Determine the Intersection Points of y = x(-x-1) with the X-axis

Quadratic X-Intercepts with Factored Form

Determine the points of intersection of the function

y=x(x1) y=x(-x-1)

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 points with the X-axis
00:03 At the intersection points with the X-axis, the Y value must = 0
00:07 Substitute Y = 0 and solve to find X values
00:13 Find what makes each factor in the product zero
00:16 This is one solution
00:23 This is the second solution
00:28 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

Determine the points of intersection of the function

y=x(x1) y=x(-x-1)

With the X

2

Step-by-step solution

To solve for the x-intercepts of the function y=x(x1) y = x(-x-1) , we set y y to zero and solve the equation x(x1)=0 x(-x-1) = 0 .

Step 1: Identify that the equation is already factored. Set each factor equal to zero:

  • x=0 x = 0
  • x1=0 -x-1 = 0

Step 2: Solve for x x in each case:
For x=0 x = 0 , the solution is x=0 x = 0 .
For x1=0 -x-1 = 0 , add 1 to both sides to get x=1 -x = 1 , then multiply by -1 to find x=1 x = -1 .

Thus, the points of intersection with the x-axis are at x=0 x = 0 and x=1 x = -1 .

Final Coordinates: Because these are x-intercepts, for both points, the y-coordinate is 0. Therefore, the points of intersection are (1,0) (-1, 0) and (0,0) (0, 0) .

The correct choice from the given options is (1,0),(0,0)( -1, 0 ), ( 0, 0 ).

3

Final Answer

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

Key Points to Remember

Essential concepts to master this topic
  • X-Intercept Rule: Set y = 0 to find where graph crosses x-axis
  • Zero Product Property: If x(x1)=0 x(-x-1) = 0 , then x = 0 or -x-1 = 0
  • Verify: Check both points: (0,0) and (-1,0) have y-coordinate = 0 ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting y-coordinate is zero for x-intercepts
    Don't write points like (0,1) or (-1,-1) for x-intercepts = points not on x-axis! X-intercepts are where the graph touches the x-axis, so y must equal zero. Always write x-intercepts as (x,0) with zero as the y-coordinate.

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 I set y = 0 to find x-intercepts?

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X-intercepts are points where the graph crosses the x-axis. On the x-axis, all points have y-coordinate = 0. Setting y = 0 finds the x-values where this happens!

How do I use the zero product property here?

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When you have x(x1)=0 x(-x-1) = 0 , the product equals zero only if at least one factor equals zero. So either x = 0 OR (-x-1) = 0, giving you both solutions!

What if I expand the function first instead?

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You could expand to get y=x2x y = -x^2 - x , then solve x2x=0 -x^2 - x = 0 . But keeping it factored as x(x1)=0 x(-x-1) = 0 is much easier and faster!

How do I solve -x - 1 = 0?

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Add 1 to both sides: x=1 -x = 1 . Then multiply both sides by -1 to get x=1 x = -1 . Remember to flip the sign when multiplying by negative!

Can I check my answer by plugging back in?

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Absolutely! For x = 0: y=0(01)=0 y = 0(-0-1) = 0 ✓. For x = -1: y=1((1)1)=1(0)=0 y = -1(-(-1)-1) = -1(0) = 0 ✓. Both give y = 0!

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