(a-5)(a+1)/a-5a/(a²+a)=(a-5)(a+1)/a-5/(a+1)=[(a-5)(a+1)²-5]/[a(a+1)]=[(a-5)(a²+2a+1)-5)]/[a(a+1)]=(a³+2a²+a-5a²-10a-5)/[a(a+1)]=(a³-3a²-9a-10)/[a(a+1)]