I am pretty new in statistics. I Googled the multivariate Gaussian distribution, but still have no idea how to solve this.
I tried to make $\mu_{x} \rightarrow a\mu_{x} \ and\, \mu_{y} \rightarrow b\mu_{y}$, is this the answer?
$\left ( X,Y \right )\sim N(\mu,\sum )\\ \mu =\begin{bmatrix} \mu _{x} \\ \mu _{y} \end{bmatrix} \ and \, \sum= \begin{bmatrix} a^{2}\mu_{x}^{2}& abCOV[X,Y]\\ abCOV[X,Y]& b^{2}\mu_{y}^{2} \end{bmatrix}$