SOLUTION: Let x and y be real numbers whose absolute values are different and that satisfy x^3 = 20x + 7y y^3 = 7x + 20y Find xy.

Question 1096469: Let x and y be real numbers whose absolute values are different and that satisfy
x^3 = 20x + 7y
y^3 = 7x + 20y
Find xy.
Answer by greenestamps(13219) (Show Source): You can put this solution on YOUR website!

An unusual problem; I don't recall seeing anything quite like it before....

Add the two equations and do some algebra:

<-- equation (1)

Then subtract the two equations and do some similar algebra:

<-- equation (2)

Now subtract equation (1) from equation (2):

Answer: xy = -7

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