Answer
vertex: $( -3,-16)$
Work Step by Step
Consider the equation: $y=x^2+6x-7$ ...(1)
The standard equation of the parabola is: $y=a(x-h)^2+k$ with vertex$(h,k)$
Consider right side $x^2+6x=7$
To complete the square add $(\frac{b}{2})^2=(\frac{6}{2})^2=9$.
$x^2+6x+9=7+9$
$(x+3)^2=16$
Thus, equation becomes:
$y=(x+3)^2-16$
Compare it with the standard form of the parabola, we get
vertex: $( -3,-16)$
