在英语中，"你背过了没用"的意思可以用以下表达来表达：
"You memorized it for nothing."
"Your memorization was in vain."
"Your memorization was wasted."
这些表达都是来自英语中的常用词汇和短语，用来表示某一个动作或者结果是没有任何意义或者没有任何用途的。
下面是一些例句和中文翻译：
"I spent hours memorizing the pst of words for the spelpng test, but I still got an F. My memorization was for nothing."
我花了几个小时背单词表，但我还是拿了个 F。我背单词是没有用的。
"I worked so hard on my presentation, but nobody paid attention. My efforts were in vain."
我花了很多功夫做我的演讲，但没人注意。我的努力都白费了。
"I studied for hours to prepare for the exam, but I still failed. All that studying was wasted."
我花了几个小时学习准备考试，但我还是没过。所有学习都白费了。