Question 164879
You first have to complete the square. 

0=x^2+6x-2
Add 2 to both sides

2=x^2+6x

Take the 6 and half it. Then take the value in this case it is 3 and square it.add 9 to both sides.

2+9=(x+3)^2
0=(x+3)^2-11

The vertex is at (3,-11)

*[invoke quadratic "x", 1, 6, -2]