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If 〖(x+y)〗2 = 144 and 〖(x-y)〗2 = 64, what is the value of xy?
We first expand each binomial to get x2 + 2xy + y2 = 144 and x2 - 2xy + y2 = 64. We then subtract the second equation from the first to find 4xy = 80. Finally, we divide each side by 4 to find xy = 20.
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