To answer part 1. in each case, integrate and set that equal to ONE.
Then solve for your c.
For each of the following functions, (1) find the constant, (2) find the c.d.f. F(x), (3) sketch graphs of f(x) and F(x) and (4) find mu and sigma squared.
1. f(x) = x^2/3, 0 < x < c
2. f(x) = (3/16) x^4; -c < x < c
3. f(x) = 1/(cx)^(1/2), 0 < x < 1 (unbounded!)
Part 2 is found using the definition .
Part 3 is basic graphing.
Part 4 is done using the basic definitions and where (it's assumed that you know how to integrate).
If you need more help then please show what you've done and where exactly you get stuck.