To find the x value of the vertex we do:
x =

if your quadratic function is in the form ax² + bx + c = y
x =

x =

Now we plug this x into the equation and solve for y.
y =

y =

y =

y =

y =

y =

Your vertex (if my math is correct) is at
You take three fourths of 270 and add it to 270. 270 + 67.5 = 337.5