(a-b)^3m*(b-a)^2m÷(b-a)^5m
=(a-b)^3m*(a-b)^2m÷(a-b)^5m*(-1)^5m
=(a-b)^5m÷(a-b)^5m*(-1)^5m
=1/(-1)^5m
=(-1)^5m