SOLUTION: x^3+x^2-20x<0

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Question 348753: x^3+x^2-20x<0
Found 2 solutions by Fombitz, stanbon:
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
x%5E3%2Bx%5E2-20x%3C0
x%28x%2B5%29%28x-4%29%3C0
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Look for regions where the function is below the x-axis.
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Solution region:(-infinity,-5) U (0,4)

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
x^3+x^2-20x<0
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Find the boundary values:
Solve x^3+x^2-20x = 0
x(x^2+x-20) = 0
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x(x+5)(x-4) = 0
x = -5 or x = 0 or x = 4
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To solve the inequality:
1st: Draw a number line and plot -5,0,4
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2nd: Test a check point from each interval
in the inequality to find the solution areas.
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x(x+5)(x-4) < 0
Test x = -10: you get -*-*- < 0 ; true
Test x = -2 : you get -*+*- < 0 ; false
Test x = 2 : you get +*+*- < 0 ; true
Test x = 10 ; you get +*+*+ < 0 ; false
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Solution: (-oo,-5)U(0,4)
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Cheers,
Stan H.
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