Question 977639
{{{y=a(x-(-3))^2+(-14)}}} Direct use of standard form.


{{{y=a(x+3)^2-14}}}

{{{a(x+3)^2=y+14}}}

{{{a=(y+14)/(x+3)^2}}}


Use the given  (0,13).
{{{a=(13+14)/(0+3)^2}}}
{{{a=27/9}}}
{{{a=3}}}


Solve this for x:
{{{y=3(x+3)^2-14=0}}}