Solve, inequalities...... (x+20)(x-6)(x+1) > 0?

The expression = 0 at x = -20, -1, 6
Consider the following cases
Case 1: x < -20
x+20 < 0
x-6 < 0
x+1 < 0
Thus the expression is a product of three negative numbers.
Therefore, the expression < 0

Case 2: -20 < x < -1
x+20 > 0
x-6 < 0
x+1 < 0
Thus the expression is the product of two negative and one positive numbers.
Therefore, the expression > 0

Case 3: -1 < x < 6
x+20 > 0
x-6 < 0
x+1 > 0
Thus the expression is the product of two positive and one negative numbers.
Therefore, the expression < 0

Case 4: x > 6
x+20 > 0
x-6 > 0
x+1 > 0
Thus the expression is the product of three positive numbers.
Therefore, the expression > 0

Ans: {x| -20 < x < -1 or x > 6}

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(x + 20)(x - 6)(x + 1) > 0

x + 20 > 0
x > -20

x - 6 > 0
x > 6

x + 1 < 0
x < -1

∴ -20 < x < -1, x > 6

-20<x<-1 or x>6

x>6
-20<x<-1
-19<=x<=-2