Đáp án+Giải thích các bước giải:
`a)9x^5-x^3+2x^2-x`
`=x(9x^4-x^2+2x-1)`
`=x[9x^2-(x^2-2x+1)]`
`=x[(3x)^2-(x-1)^2]`
`=x(3x-x+1)(3x+x-1)`
`b)x^4+2x^3-4x^2-8x`
`=x(x^3+2x^2-4x-8)]`
`=x[(x^3+2x^2)-(4x+8)]`
`=x[x^2(x+2)-4(x+2)]`
`=x(x+2)(x^2-4)`
`=x(x+2)(x+2)(x-2)`
`=x(x+2)^2 (x-2)`
`c)3x^5 y+6x^3 y+3xy`
`=3xy(x^4+2x^2+1)`
`=3xy(x^2+1)^2`
`d)x^4+2x^2-24`
`=(x^4+2x^2+1)-25`
`=(x^2+1)^2-5^2`
`=(x^2+1-5)(x^2+1+5)`
`=(x^2-4)(x^2+6)`
`=(x-2)(x+2)(x^2+6)`
`e)a^2-4ab+3b^2`
`=(a^2-ab)-(3ab-3b^2)`
`=a(a-b)-3b(a-b)`
`=(a-b)(a-3b)`
`f)x^4+2x^3-6x-9`
`=(x^4-3x^2)+(2x^3-6x)+(3x^2-9)`
`=x^2(x^2-3)+2x(x^2-3)+3(x^2-3)`
`=(x^2-3)(x^2+2x+3)`