Question

(a+b)³+(a-b)³-2a(a²+3b²)

Answer 1

=\(a^3+3a^2.b+3a.b^2+b^3+a^3-3a^2.b+3a.b^2-b^3-2a^3-6a.b^2=0\)

Answer 2

\(\left(a+b\right)^3+\left(a-b\right)^3-2a\left(a^2+3b^2\right)\)

\(=a^3+3a^2b+3ab^2+b^3+a^3-3a^2b+3ab^2-b^3-2a\left(a^2+3b^2\right)\)

\(=2a^3+6ab^2-2a\left(a^2+3b^2\right)\)

\(=2a^3+6ab^2-2a^3-6ab^2\)

\(=2a^3-2a^3\)

\(=0\)

Answer 3

chỉ cần áp dụng các hđt là đc