〜んじゃない？

それ、違うんじゃない？

Sore, chigau n ja nai?

That is not right, is it?

んじゃない floats your view as a question — gentler than asserting it

もう帰ってもいいんじゃない？

Mō kaette mo ii n ja nai?

Surely we can head home now?

It proposes while leaving the call to the other person

語尾を下げると、断定に近づきます。

Gobi o sageru to, dantei ni chikazukimasu.

With a falling tone it edges toward an assertion.

The same sentence asks on a rise and concludes on a fall