SOLUTION: If x-y=8 and xy=7, then x^3-y^3= Show solution step by step 660 670 680 690

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Question 1133675: If x-y=8 and xy=7, then x^3-y^3=
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Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


A common type of question on a competitive math test....

Use the factorization pattern for x^3-y^3 and use the given information to evaluate the resulting factors.
x^3-y^3 = (x-y)(x^2+xy+y^2)
        = (x-y)((x^2-2xy+y^2)+3xy)
        = (x-y)((x-y)^2+3(xy)

You are given the values of (x-y) and (xy); plug them in to find the answer.