Question

Giúp mình với

Answer 1

2: Ta có: \(B=\left(x-3\right)\left(x+3\right)\left(x+2\right)-\left(x-1\right)\left(x^2-3\right)-5x\left(x+4\right)^2-\left(x-5\right)^2\)

\(=\left(x^2-9\right)\left(x+2\right)-\left(x^3-3x-x^2+3\right)-5x\left(x^2+8x+16\right)-\left(x^2-10x+25\right)\)

\(=x^3+2x^2-9x-18-x^3+x^2+3x-3-5x\left(x^2+8x+16\right)-\left(x^2-10x+25\right)\)

\(=3x^2-6x-21-5x^3-40x^2-80x-x^2+10x-25\)

\(=-5x^3-38x^2-76x-46\)