Question 563568: Solve the inequality
x^2+13x>-36
What I did:
x^2+13x>-36 (add 36 to both sides)
x^2+13x+36>0 (Then I factored)
(x+4)(x+9) (this becomes)
x=-4 x=-9 (now I am stuck)
it is either (-9,-4) or (-Inf,-9)U(-4,Inf) I can't figure it out
Answer by richard1234(7193)   (Show Source):
You can put this solution on YOUR website! We have (x+4)(x+9) > 0. What you would do is test certain values of x to see which intervals satisfy. For example, suppose x = -5. Then (-5+4)(-5+9)>0, a false statement. Hence the answer is (infinity, -9) U (-4, infinity).
The other method to do is it note that (x+4)(x+9) is a parabola that opens upward, so the part between the roots -4, -9 would be below the x-axis.
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