a) \(\left(x^2-2x+1\right).\left(x-1\right)\)
\(=x^2.x+x^2.\left(-1\right)+\left(-2x\right).x+\left(-2x\right).\left(-1\right)+1.x+1.\left(-1\right)\)
\(=x^2-x^2-2x^2+2x+x\)
b) \(\left(x^3-2x^2+x-1\right).\left(x-2y\right)\)
\(=x^3.x+x^3.(-2y)+(-2x^2).x+(-2x^2).(-2y)+x.x+x.(-2y)+(-1).x+(-1).(-2y)\)
\(=x^4-2x^3y-2x^3+4x^2y+x^2-2xy-x+2y\)
Tự rút gọn -.-