Question 2128
{{{y=-9x^2}}}
<br>
Anytime the x^2 term is a negative it is going to open down.  Anytime the x^2 term is positive it is going to open up.
So, <b>this parabola opens down.</b>
<br>
Since there is only 1 term, which is 9x^2, we really can't complete the square.  However, we could say {{{y=9(x+0)^2+0}}}.  This is in the form of y=a(x-h)^2+k, where (h,k) is the vertex and x=h is the axis of symmetry.  
<br><b>So, (0,0) is the vertex...
x=0 is the axis of symmetry.</b>
<br>
Here is the graph to prove my statements...
{{{graph( 400, 200, -.625, .625, -.625, .625, -9 x^2)}}}
MS