Originally Posted by

**exphate** Hey all,

Sorry if this is in the wrong spot, it just seemed to not fit elsewhere.

I'm having trouble with proving a binary operation, having just started the subject. I'm trying to do this question:-

"X = {(x,y):y=2x} subset $\displaystyle R^2$ and the map o: X x X --> $\displaystyle R$ is given by o: {(x,y), (a,b) = (x+a, y+b)}. Show that o is a binary operation and that (X,o) is a group."

Now, I know that to be a group, it needs to be associative, have an identity and an inverse, but I'm struggling with proving the binary operation part.

Can anyone provide some tips please?