I have this question in the form

$\displaystyle 3y^2+[6y^2+(3y-4)]$

It just tells me to write this in its simplest form. So I have done

$\displaystyle 3y^2+[-6y^2-(-3y-4)]$

$\displaystyle 3y^2-6y^2+3y-4$

$\displaystyle -3y^2+3y-4$

Is this in its simplest form? I think I have turned it into a quadratic now right? So should I try to solve it using the quadratic formula?