a^2/(a^-4)+4/(a+2-a^2)+(4a-4)/(a^4-5a^2+4)=a^2/(a-2)(a+2)-4/(a-2)(a+1)+4/(a+1)(a-2)(a+2)=(a^2(a+1)-4(a+2)+4)/(a+1)(a-2)(a+2)=(a^3+a^2-4a-4)/(a+1)(a-2)(a+2)=(a+1)(a-2)(a+2)/(a+1)(a-2)(a+2)=1
