Question 918238
I'm assuming you mean {{{f(x)=-2x^2-12x-16}}}
Convert to vertex form by completing the square.
{{{f(x)=-2(x^2+6x)-16}}}
{{{f(x)=-2(x^2+6x+9)-16+18}}}
{{{f(x)=-2(x+3)^2+2}}}
(-3,2) is the vertex.