(x-y)^2-(x+y)^2=-4xy докажите тождество

Question

(x-y)^2-(x+y)^2=-4xy докажите тождество

Answer 1

(x-y)^2-(x+y)^2=-4xy

(x-y)^2-(x+y)^2=

=(x-y-(x+y))*(x-y+x+y)=

=(x-y-x-y)*2x=

=(-2y)*2x=

=-4xy


-4xy=-4xy

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