Question

A=( x + 3)^2 + ( x - 3 ) ( x + 3 ) - 2 ( x^2 + 2)( x - 4 )

Answer 1

\(A=\left(x+3\right)^2+\left(x-3\right)\left(x+3\right)-2\left(x^2+2\right)\left(x-4\right)=x^2+6x+9+x^2-9-2\left(x^3-4x^2+2x-8\right)=2x^2+6x-2x^3+8x^2-4x+16=-2x^3+10x^2+2x+16\)

Answer 2

Ta có: \(A=\left(x+3\right)^2+\left(x-3\right)\left(x+3\right)-2\left(x^2+2\right)\left(x-4\right)\)

\(=x^2+6x+9+x^2-9-2\left(x^3-4x^2+2x-8\right)\)

\(=2x^2+6x-2x^3+8x^2-4x+16\)

\(=-2x^3+10x^2+2x+16\)