Đáp án + Giải thích các bước giải:
`a)5x(x-2y)+2(2y-x)^2=5x(x-2y)-2(x-2y)^2`
`=(x-2y)[5x-2(x-2y)]=(x-2y)(5x-2x+2y)`
`=(x-2y)(3x+2y)`
`b)9x(x-y)-10(y-x)^2=9x(x-y)+10(x-y)^2`
`=(x-y)[9x+10(x-y)]=(x-y)(9x+10x-10y)`
`=(x-y)(19x-10y)`
`c)(4x-8)(x^2+6)-(4x-8)(x+7)+9(8-4x)`
`=(4x-8)(x^2+6)-(4x-8)(x+7)-9(4x-8)`
`=(4x-8)(x^2+6-x-7-9)=(4x-8)(x^2-x-10)`
d)100x^2-(x^2+25)^2=(10x)^2-(x^2+25)^2`
`=(10x-x^2-25)(10x+x^2+25)`
`=-(x^2-10x+25)(x^2+10x+25)`
`=-(x-5)^2(x+5)^2`
`e)(x+y-5)^2-2(x+y-5)+1`
`=(x+y-5)^2-2.(x+y-5).1+1^2`
`=(x+y-5-1)^2=(x+y-6)^2`
