t^3-3t-2>0
(t^3-t)-(2t+2)>0
t(t^2-1)-2(t+1)>0
t(t+1)(t-1)-2(t+1)>0
(t+1)(t^2-t-2)>0
(t+1)(t-2)(t+1)>0
(t+1)^2*(t-2)>0
因为：(t+1)^2>=0
所以：t-2>0
即：t>2