Question

if i hadn't taken your advice,i would have made a

great mistake.中为什么要用would have made

Answer 1

这是英语中的虚拟语气用法。

句意为：如果我（当初）没有采纳你的建议，我就可能已经犯了一个巨大的错误。

很明显，此句为对过去情况的假设。所以根据相关语法规定，if此句采用过去完成时，而主句谓语则由“would have done”构成，所以答案用would have made