сократить выражение b/(a-1)^2-ba^2/(1-a)^2

b/(a-1)^2-a^2b/(-(a-1))^2=(-(a-1))^2*b-a^2b*(a-1)^2/(-(a-1))^2*(a-1)^2=(a-1)^2*b-a^2b*(a^2-2a+1)/(a-1)^2*(a-1)^2=(a^2-2a+1)b-a^4b+2a^3b-a^2b/(a-1)^4=a^2b-2ab+b-a^4b+2a^3b-a^2b/(a-1)^4=-2ab+b-a^4b+2a^3b/(a-1)^4