Đáp án:
`a=(x+y)(x-8)`
`b=(-3x-1)(9x-1)`
bài 2: `x=6;x=-4`
Giải thích các bước giải:
`a,x^2+xy-8x-8y`
`=(x^2+xy)-(8x+8y)`
`=x(x+y)-8(x+y)`
`=(x+y)(x-8)`
`b,9x^2-6x+1-36y^2`
`=(9x^2-6x+1)-36x^2`
`=(3x-1)^2-(6x)^2`
`=(3x-1-6x)(3x-1+6x)`
`=(-3x-1)(9x-1)`
Bài 2:
`x^2-2x+1=25`
`⇔(x^2-2x+1)-25=0`
`⇔(x-1)^2-5^2=0`
`⇔(x-1-5)(x-1+5)=0`
`⇔(x-6)(x+4)=0`
⇔\(\left[ \begin{array}{l}x-6=0\\x+4=0\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=6\\x=-4\end{array} \right.\)
Vậy `x=6;x=-4`