for和since的用法
题目
for和since的用法
答案
for +一段时间
since +句子
since +一段时间+ ago
since +时间点
例如 he has been dead for three years
he has been dead since three years ago
He has studied English since 2003
He has studied English since he was ten years old
举一反三
已知函数f(x)=x,g(x)=alnx,a∈R.若曲线y=f(x)与曲线y=g(x)相交,且在交点处有相同的切线,求a的值和该切线方程.
我想写一篇关于奥巴马的演讲的文章,写哪一篇好呢?为什么好
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