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