How to use Cauchy Riemann

I have reached a step in the question where I have to apply the Cauchy Riemann formulas to:

$\displaystyle (-6x-2By)^2+(-12x+4By)i$

How would I apply the Cauchy Riemann formula to answer the rest of the question?

And how would I know if it is analytic?

The cauchy-riemann formula:

The function f(z)= g(x,y)+ h(x,y)i is differentiable with respect to z= x+ iy only if it satisfies the "Cauchy-Riemann equations":

$\displaystyle \frac{\partial g}{\partial x}=\frac{\partial h}{\partial y}$

and

$\displaystyle \frac{\partial g}{\partial y}=-\frac{\partial h}{\partial x}$