Solve Probability Questions: Find E[X], E[2^X], & More

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probabilty question please help!

i need full working out process...
thanks for helping me :)
1. Let X be a random variable with PMF
x 0 1 2 3 4
p(x) 5k 4k 3k 2k k

(a) Find k.
(b) Find E[X] and var(X).
(c) Find E[2^X].

2. The joint PMF of X and Y is pX;Y (x; y) = c(x2 + y2), x; y = 1; 2; 3. Find
(a) c and the marginal PMFs of X and Y
(b) E[X]
(c) The PMF of 3X - 2Y
(d) E[3X - 2Y ] in two ways.
 
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