Is a novel written

Are these sentences correct:

1-This is a computer repaired yesterday.
(This is a computer that was repaired yesterday.)

2-This is a rock band formed in the nineties.
(This is a rock band that was formed in the nineties.)

3-"War and Peace" is a novel written in the nineteenth century.
("War and Peace" is a novel that was written in the nineteenth century.)

I think the sentences are correct, but I tend to use the version with 'that was'.

Gratefully,
Navi.