Đáp án + Giải thích các bước giải:
a) `3x^2-6x=3x.x-3x.2=3x.(x-2)`
b) `x^2-2x+1-y^2=x^2-2.x.1+1^2-y^2=(x-1)^2-y^2=(x-1-y)(x-1+y)`
c) `9x^3-9x^2y-4x+4y=(9x^3-9x^2y)-(4x-4y)=(9x^2 .x-9x^2 .y)-(4.x-4.y)=9x^2(x-y)-4(x-y)=(x-y)(9x^2-4)=(x-y)[(3x)^2-2^2]=(x-y)(3x-2)(3x+2)`
d) `x^3-2x^2-8x=x^2 .x-2x.x-8.x=x(x^2-2x-8)=x(x^2-4x+2x-8)=x(x.x-4.x+2.x-2.4)=x[x(x-4)+2(x-4)]=x(x-4)(x+2)`
