Question

Without your help, we could not have succeeded.

句子后面的 we could not have succeeded可以换成we would ntot have succeeded吗？
不是应该用虚拟语气吗？那could not 为什么是对的？

Answer 1

Without your help we would not have succeeded 可以的，在这里could和would意思一样。
例句：
But for his help,we would be working now.
要不是他的帮助，我们还会在工作呢。
Without your instruction,I would not have made such great progress.
要是没有你的指导，我不会取得如此大的进步。

Answer 2

不可以，因为could not have succeeded表示他已经成功了，而would表示对将来的虚拟，很明显不符合逻辑。

Answer 3

不行的。根据语境：没有你的帮助，我们就【不可能】成功。
换成would not have succeeded 就不通顺。
could not have done sth就是虚拟语气，意为：本不可能.....