a) =x3-2x2+6x2-12x -12x +24
= x2(x-2)+6x(x-2)-12(x-2)
= (x-2)(x2+6x-12)
mk giải đc câu a thôi, bn zô jup mk lại vs
\(a,x^3+4x^2-24x+24\)
\(=x^3+6x^2-12x-2x^2-12x+24\)
\(=\left(x^3-2x^2\right)+\left(6x^2-12x\right)-\left(12x-24\right)\)
\(=x^2\left(x-2\right)+6x\left(x-2\right)-12\left(x-2\right)\)
\(=\left(x-2\right)\left(x^2+6x-12\right)\)
b)
x8+x4+1
= x8+x7+x6-x7-x6-x5+x5+x4+x3-x3-x2-x+x2+x+1
= x6(x2+x+1)-x5(x2+x+1) +x3(x2+x+1)-x(x2+x+1)+(x2+x+1)
= (x2+x+1)(x6-x5+x3-x+1)
= (x2+x+1)(x6-x5+x4-x4+x3-x2+x2-x+1)
= (x2+x+1)[x4(x2-x+1) - x2(x2-x+1) + (x2-x+1)]
= (x2+x+1)(x2-x+1)(x4-x2+1)
