Well the answer is 1/3 which i cannot seem to get.Suppose that P(X=0)=1-P(X=1). If E[X]=3Var(X), nd P(X=0).

I calculate P(X = 1) = p

thus P(X = 0) = 1 - p

Var(x) = (1 - p)/p^2

E(x) = 1 / p

Solving this u get

p = 3(1 - p) and thus p = 3/4...so P(x = 0) = 1/4 and not 1/3 which is the answer.

Any help would be appreciated.

Thank-you