化简3x^2-9x-12/x^2+2x+1 xy-x-y+1/y^2-2y+1化简约分(1)3x^2-9x-12/x^2+2x+1 (2)xy-x-y+1/y^2-2y+1

(2)①xy-x-y+1
提取公因子 x 得 x（y-1）-y+1
变式 得 x（y-1）+（y-1）
提取公因式（y-1）得 xy-x-y+1=（x+1）*（y-1）
②y^2-2y+1
根据 十字相乘法 将式子进行如下拆分 y - 1
y - 1
所以 y^2-2y+1=（y-1）^2
所以(xy-x-y+1)/(y^2-2y+1 )
=[（x+1）*（y-1）] /[（y-1）^2]
=（x+1)/(y-1)

(3x^2-9x-12)/(x^2+2x+1)
= 3(x^2-3x-4)/(x+1)^2
= 3(x-4)(x+1)/(x+1)^2
= 3(x-4)/(x+1)

3x^2-9x-12/x^2+2x+1
=3(x^2-3x-4)/(x+1)^2
=3(x-4)(x+1)/(x+1)^2
=3(x-4)/(x+1)
xy-x-y+1/y^2-2y+1
=xy-y-x+1/(y-1)^2
=y(x-1)-(x-1)/(y-1)^2
=(x-1)(y-1)/(y-1)^2
=(x-1)/(y-1)

(3x^2-9x-12)/(x^2+2x+1)
= 3(x^2-3x-4)/(x+1)^2
= 3(x-4)(x+1)/(x+1)^2
= 3(x-4)/(x+1)
(xy-x-y+1)/(y^2-2y+1)
=(x-1)(y-1)/(y-1)^2
=(x-1)/(y-1)