Question 704344
Standard form will give a path to finding an equation you want.  The vertex corresponds to values you find in the standard form quadratic equation.  


{{{y=a(x-h)^2+k}}} is a way of expressing standard form for a parabola.  The vertex is at (h,k).  Just fit them in how they belong in the equation from your given vertex point of (3, 9).  Because h=3, and k=9, you have {{{y=a(x-3)^2+9}}}.  


What's left?  You have a point on the graph given as the origin, (0,0).  If you fill in h, k, and the coordinates of the origin point, you will be able to solve for the coefficient, a.  You SHOULD find that a is less than zero.  The vertex is a maximum point of the parabola.