帮忙用因式分解法解下列方程.麻烦写出解题过程与思路.

①x^2-y^2+a^2-b^2+2ax+2by
=x^2+2ax+a^2-b^2+2by-y^2
=(x+a)^2-(b-y)^2
=(x+a+b-y)(x+a-b+y)
②4-（x^2-4x+2)^2
=(2+x^2-4x+2)(2-x^2+4x-2)
=(x^2-4x+4)(-x^2+4x)
=[(x-2)^2][-x(x-4)]
=-x(x-2)^2(x-4)
③a^2-ab+ac-bc
=a(a-b)+c(a-b)
=(a-b)(a+c)
④m^2-5m-mn+5n
=m(m-5)-n(m-5)
=(m-5)(m-n)
⑤x^2-x-12
=(x-4)(x+3)

①x^2-y^2+a^2-b^2+2ax+2by
=x²+2ax+a²-（y²-2by+b²）=（x+a）²-（y-b）²=（x+a+y-b）(x+a-y+b)
②4-（x^2-4x+2)^2=2²-（x^2-4x+2)^2=（2+x^2-4x+2）（2-x²+4x-2）=（x-2）...

1.(x-a)^2-(y-b)^2