# Thread: Can someone solve a question on changing variables (matrix method)

1. ## Can someone solve a question on changing variables (matrix method)

if anyone could find me a solution to this and explain the method i would be really grateful.

2. ## Re: Can someone solve a question on changing variables (matrix method)

Hey bobby84.

If two variables are independent the covariance is 0 and thus Var[X+-Y] = Var[X] + Var[Y] +- Cov[X,Y] = Var[X] + Var[Y]. What can you conclude from this?