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Homework Statement
Calculate the marginal density of fx (x).
Fx,y (x,y) = double integral of 4x.e^(x+y) when 0<x<y, 0 otherwise.
Homework Equations
The Attempt at a Solution
i set up the equation as fx (x) = integral from x up to infinity of 4x.e^(x+y) dy
i get 4x [e^(x+y)] from x to infinity,
thats when the problem arises as whatever i do there's always infinity in the question.
I'm told the answer is 4x.e^(-2x)
any help would be really appreciated.
thanks.