It really depends on what 'c' is.
Do you mean you need to find 'c' s.t f(x) is a pmf?
Is the function f(x) = c(x+1)^2 for X = 0, 1, 2, 3, a probability mass function? Explain
why or why not. I am not exactly sure how you can tell if something is a pmf? I looked in my textbook but it doesn't really explain it so I can understand it. Thanks to anyone who can help.