You know the standard equation of a quadratic equation?
a(x-h)^2+k where (h,k) is the vertex of the parabola.
Well this is obviously a Quadratic because the graph is a downward parabola which is symetrical with respect to the y-axis.
Can you find a way to write this equation in standard form without anymore of my help?
Hint: h is the last term of your eqution!