Question

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Answer 1

a)
$(a-b)^2-(a+b)^2= \\ \\ a^2-2ab+b^2-(a^2+2ab+b^2)= \\ \\ \not a^2-2ab+\not b^2-\not a^2-2ab-\not b^2= \\ \\ -4ab$

b)
$(x+y)^2+(x-y)^2= \\ \\ x^2+\not2xy+ y^2+ x^{2} -\not2xy+ y^2= \\ \\ 2 x^{2} +2y^2$

c)
$a(a-b)^2-a(a+b)^2= \\ \\ a(a^2-2ab+b^2)-a(a^2+2ab+b^2)= \\ \\\not a^3-2a^2b+\not ab^2-\not a^3-2a^2b-\not ab^2= \\ \\ -4a^2b$