Đáp án:
`a) 4x^2-y^2+4x+1`
`=(4x^2+4x+1)-y^2`
`=(2x+1)^2-y^2`
`=(2x-y+1)(2x+y+1)`
`b) x^5-3x^4+3x^3-x^2`
`=x^2(x^3-3x^2+3x-1)`
`=x^2(x-1)^3`
`c) 36+2xy-x^2-y^2`
`=36-(x^2-2xy+y^2)`
`=6^2-(x-y)^2`
`=(6-x+y)(6+x-y)`
`d) x^3-x^2-5x+125`
`=x^3+5x^2-6x^2-30x+25x+125`
`=x^2(x+5)-6x(x+5)+25(x+5)`
`=(x+5)(x^2-6x+25)`
Giải thích các bước giải: