Question 772626
Q:
If {{{(x-y)^2=40}}} and x^2+y^2=60, then xy=?
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A:
{{{(x-y)^2 = x^2 - 2xy + y^2}}}
{{{(x-y)^2 = (x^2 + y^2) - 2xy}}}
{{{40 = 60 - 2xy}}}
{{{xy = (60 - 40)/2 = highlight(10)}}}
Answer: {{{highlight(10)}}}