how can u tell your parents that they're wrong?

It was really hard to do it. I personally encounter that situation but the easiest way is to tell them politely in low soft tone of voice with matching sweetness so that they can't really them we are correcting them. Sometimes I cite example to some other family and sometimes it really do works for me and mom.

My parent's are a bit hard headed so i have to prove them wrong. At theirs and my expense. Then they would change.

I'll find the possible politest way to correct them (don't tell they're wrong directly), although it won't be easy because they know what we've got.

I find it hard to tell them. But sometimes, I ask indirectly and use examples so that it won't be obvious.

then dont be afraid to correct them. They're also human..nobody's perfect ryt?!