Hi, I need some help with understanding bijective functions.

Is the function f(a,b) = (a+1,b) for all (a,b) bijective? I think not because x is not equal to y. Can some please help me with this?

Also similar to this,

f(a,b) = a-1 for all (a,b). Is this function onto or bijective?

Thnaks alot.