I am trying to compute $VAR(2X-3Y)$ which may be rewritten as $$E\left((2X-3Y)^2\right) - \left(E(2X-3Y)\right)^2=E(4X^2-6XY +9Y^2) - E(2X -3Y)E(2X-3Y)$$
How do I compute the rest?
2026-03-29 19:10:03.1774811403
Compute sums of variances
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You can use the results in this link: http://www.cse.cuhk.edu.hk/~cslui/ERG2040C/tutorial11_notes.pdf about the expectation of linear combinations of variables. It will help you simplify the expression you have got. After that, you will have to use the definition of expectation, depending on what is the probability distribution of your variables.