Question

chung minh rang cac bieu thuc sau khong phu thuoc vao gia tri cua bien x, biet B= x (x^3 + 2x^2 - 3x +2) - (x^2+ 2x) x^2 +3x ( x-1) +x-12

Answer 1

B=x^4+2x^3-3x^2+2x-x^4-2x^3+3x^2-3x+x-12

=-12

Answer 2

\(B=x\left(x^3+2x^2-3x+2\right)-\left(x^2+2x\right)x^2+3x\left(x-1\right)+x-12\)

\(=x^4+2x^3-3x^2+2x-x^4-2x^3+3x^2-3x+x-12\)

\(=\left(x^4-x^4\right)+\left(2x^3-2x^3\right)+\left(-3x^2+3x^2\right)+\left(2x-3x+x\right)-12\)

\(=0+0+0+0-12\)

\(=-12\)