Find the vertex of the graph of the equation x - y^2 + 8y = 13 + 2y - 4x + 15y + 3y^2.
Simplify as
5x = 4y^2 + 9y + 13
x = (4/5)y^2 + (9/5)y + 13/5
The y coordinate of the vertex = -(9/5) / (2 * 4/5) = -9/8
The x coordinate is
(4/5) (-9/8)^2 + (9/5)(-9/8) + 13/5 = 127 / 80
+506 
