Answer
vertex: $( -1,-29)$
Work Step by Step
Consider the equation: $y=x^2+2x-28$ ...(1)
The standard equation of the parabola is: $y=a(x-h)^2+k$ with vertex$(h,k)$
Consider right side $x^2+2x=28$
To complete the square add $(\frac{b}{2})^2=(\frac{2}{2})^2=1$.
$x^2+2x+1=28+1$
$(x+1)^2=29$
Thus, equation (1) becomes:
$y=(x+1)^2-29$
Compare it with the standard form of the parabola, we get
vertex: $( -1,-29)$
