# Math Help - Set Theory help..

1. ## Set Theory help..

Thank you..

2. This is not a homework service
slipz418, you have posted a set of three problems.
They are nice problems.
What do you expect from us?
Remember that this is not a homework service

3. I'll try to give you some guidance,

the definition of one-to-one is:

$\forall x,y \in \mathbb{R} f(x)=f(y) \implies x = y$

and onto:

$\forall y \in \mathbb{R} \exists x \in \mathbb{R} f(x) = y$.

Also to prove that something is not one to one you need to find $x,y\in \mathbb{R}$ such that $f(x) = f(y)$ and $x \neq y$.

Hope that helps.