Question 268324
(x-y)^2-(x+y)^2
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2 ways to do this:
You can multiply everything out, collect terms.
= x^2 - 2xy + y^2 - (x^2 + 2xy + y^2)
= -4xy
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Or, treat it as the difference of 2 squares a^2 - b^2
a^2 - b^2 = (a+b)*(a-b)
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(x-y)^2-(x+y)^2 = { (x-y) + (x+y) }*{ (x-y) - (x+y) }
= (2x)*(-2y)
= -4xy