SOLUTION: find value of x^3+y^3+12xy-64 when x+y=4

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Question 761579: find value of x^3+y^3+12xy-64 when x+y=4
Answer by ramkikk66(644) About Me  (Show Source):
You can put this solution on YOUR website!
x+%2B+y+=4
Cubing both sides of the equation
%28x+%2B+y%29%5E3+=+x%5E3+%2B+y%5E3+%2B+3%2Ax%2Ay%2A%28x%2By%29+=+4%5E3+=+64
Substituting for x+y as 4 on the left hand side
x%5E3+%2B+y%5E3+%2B+3%2Ax%2Ay%2A4+=+64
x%5E3+%2B+y%5E3+%2B+12%2Ax%2Ay+=+64
So
x%5E3+%2B+y%5E3+%2B+12%2Ax%2Ay+-+64+=+0

:)