1)(a+b)^2+(a+b)^2=(a^2+2ab+b^2)+(a^2-2ab+b^2)
=a^2+2ab+b^2+a^2-2ab+b^2
=a^2+2ab+b^2+a^2-2ab+b^2
=2a^2+2b^2
(a+b)^2+(a+b)^2 = 2(a^2+b^2)
1/2[(a+b)^2+(a+b)^2 ]= (a^2+b^2)
(a+b)^2-(a-b)^2=(a^2+2ab+b^2)-(a^2-2ab+b^2)
=a^2+2ab+b^2-a^2+2ab-b^2
=4ab
1/2[(a+b)^2+(a+b)^2 ]= ab
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