how do you find the vertex?

If you are refering to a quadratic function (a parabloola), there are various ways:

1) graph the equation and read the values from the graph

2) complete the square and get the equation into the form:  y  = a(x - h)² + k; the vertex will be (h, k)

3) use the formulas:  x = -b/(2a)    y = (b² -4ac)/(4a) to find the x- and y-values of the vertex