if $X$ and $Y$ are dependent stochastic variables where $Var(x) = 1.95$, $Var(Y)=0.9$ and $Cov(X,Y)=0.8$. Find the variance of $Z = -4X+4Y-6$
I tried using $Var(X+Y) = Var(X) + Var(Y) + 2cov(X,Y)$ where I basically tried to say $Var(-4X+4Y-6) = Var(-4X) + Var(4Y) + Var(-6) + 2Cov(-4X, 4Y)...$ but this seems like an incorrect approach and doesn't yield me the correct answer (given that my calculations are correct).
I cant find any other logical formulas in my book, only the definitions for variance and covariance.. The formula I tried I found on wolfram.