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mrkb80
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Homework Statement
Suppose that [itex]f_{X,Y}(x,y)=\lambda^2e^{-\lambda(x+y)},0\le x,0\le y [/itex]
find [itex]E[X+Y][/itex]
Homework Equations
The Attempt at a Solution
I just want to double check I didn't make a mistake:
[itex]E[X+Y]=E[X]+E[Y]=\int_0^{\infty} x{\lambda} e^{-\lambda x} dx + \int_0^{\infty} y{\lambda} e^{-\lambda y} dy = -2 - \dfrac{2}{\lambda} [/itex]
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