To talk about a past that never happened, use teria plus the past participle for the result, and se plus tivesse plus the participle for the condition. After ter the participle never changes its ending.
Examples
- Se tivesse estudado mais, teria passado no exame.
- If I had studied more, I would have passed the exam.
- Eu teria feito exatamente o mesmo.
- I would have done exactly the same.
- Nunca tinha visto nada assim.
- I had never seen anything like it.
The mistake to avoid
Agreeing the participle with the subject - after ter it stays fixed: ela teria feito, never feita.
Where this fits in
Refletir sobre a vida, Portuguese B2: Narrar experiências marcantes, falar de arrependimentos e relatar o que outros disseram com tempos compostos e discurso indireto.