pointless

It is pointless to argue with him when he has already made up his mind and won't listen.

(Chinese) 当他已经下定决心且不听劝时，和他争论是徒劳的。

Trying to vacuum the rug while the cat is shedding is a pointless task.

(Chinese) 在猫掉毛的时候尝试吸尘地毯是一项白费力气的工作。