They are Functions (well the middle one definitely is (I would have to look at the graph of the other two to see for sure). They don't really have answers per say. You could either graph these, or solve them for specific values, but there are no "answers."
Alexander Sergejev The first and third ones will be "prove by mathematical induction that...", the second one is a cumulation, so you won't be able to plot a graph of it.
There's no need to make yourself look even more stupid by replying.
Bill Hardiman You can't graph a function?! Are you serious? I'm sorry ... f(x) means what?
For the other two, you aren't actually disagreeing. There is no single answer. You can show that the mathematical statements are true, and the easiest way to do that is to input values and test it. Perhaps there is some doctorate level way to prove it more theoretically but w/e.
Alexander Sergejev In terms of proving them, I'm not sure what level you failed at, but with a AS in maths, I can prove many such terms, using a technique called mathematical induction. As I have already said.
And as for the graph, how about you plot a graph of the sum of the cubes of all real numbers. Enjoy! Whilst it is actually possible, it's a stupid idea to try.