Help with two problems please (domain and difference quotient)

I'm a little stumped on these two problems, we have to input our answers online, so I'm not sure if my answers are wrong, or if I'm just inputting them incorrectly. Here are the two problems:

Find the difference quotient of *f(x)=3x**3**+x-5*.

Just type in the expression after simplifying completely as if you were going to type it in a calculator. Do not use an =, ie, DQ = or y=. No spaces and place *x-*terms in descending order and the constant term last.

The answer I'm coming up with is: 9x^2+9xh+h^2

And the other problem is Find the domain of *https://vista8.kent.edu/webct/Relati...eq_7ddefda.gif*

Write your answer in interval notation. Use a lower case u for union, inf for https://vista8.kent.edu/webct/Relati...eq_7ddfe0a.gif, -inf for https://vista8.kent.edu/webct/Relati...eq_7ddffaa.gif , all other symbols are normal. Remember no spaces. No rounding.

To which I answer: (-inf,5)u(5,inf)

It's been awhile since i've done domain, so I'm a bit rusty.

Any help would be greatly appreciated, thanks you in advance!