3(а+в)²-(2а+в)(2а-в)

Question

3(а+в)²-(2а+в)(2а-в)

Answer 1

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Answer 2

3(a+b)^2-(2a+b)(2a-b)=
3(a^2+2ab+b^2)-4a^2+b^2=
3a^2+6ab+3b^2-4a^2+b^2=
4b^2+6ab-a^2.