### Binomial Expansion: (-x-y)^2=???

A http://www.door2math.com production.expand (-x-y)^2 ? would you write it as : x^2 + y^2 + (-2)(-x)(-y) ------ x^2 + y^2 -2xy or as : x^2 + y^2 +(2)(-x)(-y) ------ x^2 + y^2 +2xy ?

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