Answers

2014-10-07T19:53:29+05:30
It is not (a+b) ^{2} . It is (a+b+c) ^{2}
Now we will prove this.
(a+b+c)(a+b+c)= a(a+b+c)+b(a+b+c)+c(a+b+c)=a^2+ab+ac+ab+b^2+bc+ac+bc+c^2
⇒a^2+b^2+c^2+2ab+2bc+2ca
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good. your answer was best answer