(c-2ab+a+b)(a-2+b+c)+(1-ab)^2因式分解

(c-2ab+a+b)(a-2+b+c)+(1-ab)^2=(a+b+c-2ab)(a+b+c-2)+(1-ab)^2=(a+b+c)^2-2(1+ab)(a+b+c)+4ab+(1-ab)^2=(a+b+c)^2-2(1+ab)(a+b+c)+(1+ab)^2=[(a+b+c)-(1+ab)]^2=(a+b+c-1+ab)^2