Question

phân tích đa thức -x^2 - 2x + 8 thành nhân tử

Answer 1

Ta có: \(-x^2-2x+8\)

\(=-\left(x^2+2x-8\right)\)

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

\(=-\left[x\left(x+4\right)-2\left(x+4\right)\right]\)

\(=-\left(x+4\right)\left(x-2\right)\)

Answer 2

\(-x^2-2x+8\\ =-\left(x^2-4x-2x+8\right)\\ =-\left[x\left(x-2\right)-4\left(x-2\right)\right]\\ =-\left(x-2\right)\left(x-4\right)\)