Solve the Quadratic Inequality: -x² + 2x > 0

Question

Solve the following equation:

-x^2+2x>0

Video Solution

Step-by-Step Solution

To solve the inequality x2+2x>0-x^2 + 2x > 0, we begin by considering the corresponding equation x2+2x=0-x^2 + 2x = 0.

First, factor the quadratic equation:

  • Rearrange the terms: x2+2x=0-x^2 + 2x = 0 becomes x(2x)=0x(2 - x) = 0.
  • This gives us the roots x=0x = 0 and x=2x = 2.

These roots divide the number line into three intervals: x<0x < 0, 0<x<20 < x < 2, and x>2x > 2.

We need to test these intervals to determine where the inequality holds:

  • For x<0x < 0, choose a test point like x=1x = -1: the expression (1)2+2(1)=12=3-(-1)^2 + 2(-1) = -1 - 2 = -3, which is not greater than zero.
  • For 0<x<20 < x < 2, choose a test point like x=1x = 1: the expression (1)2+2(1)=1+2=1-(1)^2 + 2(1) = -1 + 2 = 1, which is greater than zero.
  • For x>2x > 2, choose a test point like x=3x = 3: the expression (3)2+2(3)=9+6=3-(3)^2 + 2(3) = -9 + 6 = -3, which is not greater than zero.

Thus, the inequality x2+2x>0-x^2 + 2x > 0 is satisfied for the interval 0<x<20 < x < 2.

Therefore, the solution to the inequality is 0<x<2\mathbf{0 < x < 2}, which corresponds to choice 2 in the given options.

Answer

0 < x < 2


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