Thread: probability density

Suppose X has density f(x) = c/(x^4) for x > 1, and f(x) = 0 otherwise, where c is a constant. Find a) c; b) E(X); c) Var(X).

I'm so confused...I dont even know where to start...

Thanks in advance!

So the integral of f(x) over all x equals 1 (since its a probability density function) so
so you need to integrate, then solve for c.


and

So you can use a similiar process to find