SOLUTION: Find and Graph the solution set. a. x^3-16x>0 b. x^2-5x<=-6

Algebra ->  Inequalities -> SOLUTION: Find and Graph the solution set. a. x^3-16x>0 b. x^2-5x<=-6      Log On


   



Question 327127: Find and Graph the solution set.
a. x^3-16x>0
b. x^2-5x<=-6

Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
x%5E3-16x%3E0
x%28x%5E2-16%29%3E0
x%28x-4%29%28x%2B4%29%3E0
Break up the number line into 4 regions:
Region 1 : (-infinity,-4)
Region 2 : (-4,0)
Region 3 : (0,4)
Region 4 : (4,infinity)
Choose a point in the region (not an endpoint).
Test the inequality.
If the inequality is satisfied, the region is part of the solution.
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.
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Region 1:x=-5
x%28x-4%29%28x%2B4%29%3E0
-5%28-5-4%29%28-5%2B4%29%3E0
-45%3E0
False, this region is not part of the solution.
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.
.
Region 2:x=-2
x%28x-4%29%28x%2B4%29%3E0
-2%28-6%29%282%29%3E0
24%3E0
True, this region is part of the solution.
.
.
.
Region 3:x=2
x%28x-4%29%28x%2B4%29%3E0
2%28-2%29%286%29%3E0
-24%3E0
False, this region is not part of the solution.
.
.
.
Region 4:x=5
x%28x-4%29%28x%2B4%29%3E0
5%281%29%289%29%3E0
45%3E0
True, this region is part of the solution.
.
.
.
The solution region is (-4,0) U (4,infinity).
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Verified graphically
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+graph%28+300%2C+300%2C+-10%2C+10%2C+-50%2C+50%2C+x%2A%28x-4%29%2A%28x%2B4%29%29%29+
.
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Similarly,
x%5E2-5x%3C=-6
x%5E2-5x%2B6%3C=0
%28x-2%29%28x-3%29%3C=0
Break up the number line into 3 regions:
Region 1 : (-infinity,2)
Region 2 : (2,3)
Region 3 : (3,infinity)
Choose a point in the region (not an endpoint).
Test the inequality.
If the inequality is satisfied, the region is part of the solution.
.
.
.
Region 1:x=0
%28x-2%29%28x-3%29%3C=0
%28-2%29%28-3%29%3C=0
6%3E0
True, this region is part of the solution.
.
.
.
Region 1:x=0
%28x-2%29%28x-3%29%3C=0
%28-2%29%28-3%29%3C=0
6%3C=0
False, this region is not part of the solution.
.
.
.
Region 2:x=2.5
%28x-2%29%28x-3%29%3C=0
%280.5%29%28-0.5%29%3C=0
-0.25%3C=0
True, this region is part of the solution.
.
.
.
Region 3:x=4
%28x-2%29%28x-3%29%3C=0
%282%29%281%29%3C=0
2%3C=0
False, this region is not part of the solution.
.
.
.
The solution region is [2,3].
Since the inequality includes the "=" the brackets denote that 2 and 3 are included as part of the solution.
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graph%28300%2C300%2C-2%2C6%2C-1%2C1%2C%28x-2%29%2A%28x-3%29%29