t=根號(hào)a
t+1/(t-1)^2 - 4t^2+4t /（t^2-1）^2
t+1/(t-1)^2 - 4t^2+4t/(t+1) ^2(t-1)^2
(t+1)^3/(t+1) ^2(t-1)^2 - 4t^2+4t/(t+1) ^2(t-1)^2
(t+1)^3-4t^2-4t/(t+1) ^2(t-1)^2
t^3-t^2-t+1/(t+1) ^2(t-1)^2
(t-1)(t^2-1)/(t+1) ^2(t-1)^2
1/t+1
1/根號(hào)a+1
答案：根號(hào)a-1/a-1 一樣的問(wèn)題啊~