Solve the Quadratic Inequality: Finding When x²+6x>0

Question

Solve the following equation:

x^2+6x>0

Video Solution

Step-by-Step Solution

To solve the inequality x2+6x>0 x^2 + 6x > 0 , follow these steps:

  • Step 1: Write the inequality in factored form.
    Express x2+6x x^2 + 6x as x(x+6) x(x + 6) .
  • Step 2: Identify the roots of the equation x(x+6)=0 x(x + 6) = 0 .
    The roots are x=0 x = 0 and x=6 x = -6 .
  • Step 3: Determine the sign of x(x+6) x(x + 6) in each interval divided by the roots.
  • Step 4: Test three intervals: x<6 x < -6 , 6<x<0 -6 < x < 0 , and x>0 x > 0 .

For x<6 x < -6 :
Pick a value such as x=7 x = -7 . Substituting, x(x+6)=(7)(7+6)=(7)(1)=7>0 x(x + 6) = (-7)(-7 + 6) = (-7)(-1) = 7 > 0 .
Thus, x2+6x>0 x^2 + 6x > 0 for x<6 x < -6 .

For 6<x<0-6 < x < 0 :
Pick a value such as x=3 x = -3 . Substituting, x(x+6)=(3)(3+6)=(3)(3)=9<0 x(x + 6) = (-3)(-3 + 6) = (-3)(3) = -9 < 0 .
Thus, x2+6x<0 x^2 + 6x < 0 for 6<x<0-6 < x < 0 .

For x>0 x > 0 :
Pick a value such as x=1 x = 1 . Substituting, x(x+6)=(1)(1+6)=1×7=7>0 x(x + 6) = (1)(1 + 6) = 1 \times 7 = 7 > 0 .
Thus, x2+6x>0 x^2 + 6x > 0 for x>0 x > 0 .

Therefore, the solution to the inequality is x<6 x < -6 or x>0 x > 0 .

Thus, the correct answer is x<6,0<x x < -6, 0 < x .

Answer

x < -6,0 < x


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