x²-49分之x-1÷x²-7x分之1-x

(x²-49)分之(x-1)÷(x²-7x)分之(1-x)
=[(x+7)(x-7)分之(x-1)]×[-(x-1)分之x(x-7)]
=-(x+7)分之x
(3m-2)分之2m÷(9m²-4)分之3·(3m+2)分之m
=(3m-2)分之2m×3分之(3m+2)(3m-2)·(3m+2)分之m
=3分之2m²
mn分之(n²-m²)÷nm分之(m²-2mn+n²)÷(m-n)分之(m+n)
=mn分之[-(m+n)(m-n)]×(m-n)²分之mn×(m+n)分之(m-n)
=-1