Question

1-(a-1\1-a)^2/a^2-a+1\a^2-2a+1

Answer 1

原式=1-(a-a²-1)²/(a-1)²×(a²-2a+1)/(a²-a+1)
=1-(a²-a+1)²/(a-1)²×(a-1)²/(a²-a+1)
=1-(a²-a+1)
=-a²+a

Answer 2

1-[a-1/(1-a)]^2/[(a^2-a+1)/(a^2-2a+1)]
=1-[(a^2-a+1)/(a-1)]^2/[(a^2-a+1)/(a-1)^2]
=1-(a^2-a+1)^2/(a-1)^2*(a-1)^2/(a^2-a+1)
=1-(a^2-a+1)
=a-a^2