Finding Covariance of simple joint DF

A joint density function is given by:

f(x, y) = kx 0 < x, y < 1

0 otherwise

Find Cov(X, Y)

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Those bounds are giving me trouble. At first I read it as 0 < x < y < 1. But I get 2 different values for k depending if I use the direction of f(x) or f(y)...

I found:

f(x) = k - kx^2 which lead to k = 3/2

f(y) = (ky^2)/2 which lead to k = 6

I'm not sure if it's possible to have 2 different values of k like that ?

E(xy) led to another problem, which k to chose ? So I must have done something wrong with those bounds...

Thanks !!!

The Answer is 0

Re: Finding Covariance of simple joint DF

Re: Finding Covariance of simple joint DF

I've got it thank you. That comma in the range threw me off :p

Re: Finding Covariance of simple joint DF

but k cannot be 0.

edit: Ignore this post. looks like your covariance is 0. I thought you were saying k=0