SOLUTION: -56=(2r-21)(r+1)

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Question 548518: -56=(2r-21)(r+1)
Answer by oberobic(2304) About Me  (Show Source):
You can put this solution on YOUR website!
-56 = (2r-21)(r+1)
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(2r-21)(r+1) = -56
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Use FOIL to expand left side.
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2r^2 +2r -21r -21 = -56
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Add 56 to both sides
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2r^2 +2r -21r -21 +56 = 0
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2r^2 -19r + 35 = 0
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factor
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(2r-5)(r-7) = 0
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roots are r=5/2 and 7
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+graph%28500%2C500%2C-10%2C10%2C-10%2C10%2C2%2Ax%5E2-19%2Ax%2B35%29+