''Would''and ''could'' are modal verbs.
''Would'' is used in conditional sentences.
What would you do if you lost your job?( present tense) >would +short infinitive
If I'd had time, I would have gone to see Graham.( past tense, like in ''would have been'' ) >would+HAVE+past participle
''Could have''=it was possible, but i didn't do it:
I could have left at ten o'clock, but i didn't.
Hmmm...was it useful even a little?
...Not a teacher.
Student or Learner