Question : For random variables and , it is given that
and
Obtain
You have got to start reading and understanding your class notes and textbook! Many of the questions you are posting are done using basic definitions and formulae. MHF is not a service for doing all your homework.
This question is nothing more than applying a basic formula:
Cov(X, Y + Z) = Cov(X, Y) + Cov(X, Z).
See here: Covariance - Wikipedia, the free encyclopedia