I have that $$ X_2|X_1 = Bin(n,p) $$ and $$ X_1 = Geo(\frac{1}{B+1}) $$
I need to find the marginal distribution of $$X_2$$
I know that the joint distribution is given by $$P(X_1,X_2) = P(X_2|X_1)P(X_1)$$
I'm thinking to take the marginal I need to take the sum over X1 however it is getting messy very quickly. Is this the correct approach?
Any tips would be appreciated.