using the function f(x)=x^2+6x+5, find the y value of the vertex
Keeping in mind the fact that this equation is in the form
of y = ax^2 + bx + c, we find the y coordinate of the
vertex with the formula (- (b^2 - 4ac)/4a).
y = - (6^2 - (4 * 1 * 5)) / (4 * 1)
y = - (36 - 20) / 4
y = -16 / 4
y = -4