1. Do they seem to have been taught a different method for something you remember? Not a problem: get them to #teach you theirs, and encourage them to try to understand yours. See if you can spot similarities. Why do both work? Can you find reasons why one may be "better" than the other (there are no right answers here, but just being more familiar doesn't count)?
2. Are they doing something you don't recognise, or maybe you do recognise but never got the hang of it? Get them to #teach you as much of it as they can. Work together on it. Admit that you don't understand it YET but don't use this as an excuse to not engage. Learning new things is a positive thing. Not understanding something is a prerequisite for learning something new.
4. That's not just in front of your children, either: stop doing it with other adults. Better still, challenge other adults to stop doing it. If you want your child to succeed in #maths you MUST genuinely have a positive attitude towards it, not just fake it in front of them.
Challenging adults to stop being openly negative about maths is hard because it's a pretty sore spot for some & we don't want to make anything worse (or start an argument). But leaving it to fester isn't good either.
So when *you* call out public negativity towards maths... How?
Sometimes I like to dig around a bit and find out what they actually *mean*. "I [hate\am bad at\etc] maths" doesn't really contain much info when you think about it: what do you mean by "maths"? How would you recognise it if it entered the room? What are your criteria for not being able to "do" it? What does "doing" and "not doing" maths look like to you? What do you think the difference is between people who "can do maths" and those who "can't do maths"?
@TeaKayB there was a lot of interesting discussion already about communicating with parents. There is a pressing need to communicate how to support ss at home and some structured opportunities to talk about this (which others dug into) But when I read this post I first saw the part above about convincing math haters and I'd like to speak to that general point. First, like all opinions you have to accept you will not win over everyone. And also like in general there is a time and place for such discussions. Most casual conversations are probably not the right one and it's best handled with a small gesture that you have a different opinion, normalizing this attitude is not universal.
Ultimately, I think we need more positive modeling of interest in math and integration of math into daily life and culture rather than attempts at directly explaining "don't say I hate math". There's more bang for the buck, in a cool demo or talk that you excitedly tell others about, wearing a math themed shirt, a TV special about a mathemetician, putting up a picture of math art, etc than in direct lectures trying to change minds.
@benleis
I think that's part of it, though: it's normal to say "eurgh, I hate maths" where saying something similar with an equivalent level of vitriol about almost any other interest or hobby would be viewed as a bit weird at best.