Đáp án:
Giải thích các bước giải:
`a,x^2+6x+5`
`=x^2+x+5x+5`
`=x(x+1)+5(x+1)`
`=(x+1)(x+5)`
`b,(x^2-x+1)(x^2-x+2)-12`
`=(x^2-x+\frac{3}{2}-\frac{1}{2})(x^2-x+3/2+1/2)-12`
`=(x^2-x+3/2)^2-1/4-12`
`=(x^2-x+3/2)^2-49/4`
`=(x^2-x+3/2+7/2)(x^2-x+3/2-7/2)`
`=(x^2-x+5)(x^2-x-2)`
`=(x^2-x+5)(x^2+x-2x-2)`
`=(x^2-x+5)[x(x+1)-2(x+1)]`
`=(x^2-x+5)(x+1)(x-2)`