f(x) = c (9/10)^x-1 for x = 1,2,... . (a) Determine the constant c.

Question

I understand that the summation of f(x)=1 where it can only be 1 because thats the entire sample space

Answer 1

You have to say something more about f(x); is it a density? continuous or discrete?

If you'd like the sum of f(x) over all possible values of x to be equal 1, then c=1/10.