Question 1106268

The vertex form of a parabola is  {{{ y = a(x-h)^2 - k }}} where (h,k) = coordinates of the vertex

The vertex is given to be at (0,0), simplifying the above to {{{ y = ax^2 }}}

Picking one of the other two points (1,-2) allows us to find a:  
                  {{{  -2 = a*(1)^2 }}}
                  {{{ a = -2 }}}     —>   {{{ highlight(y = -2x^2 ) }}}

Since a<0, the parabola opens downward