Chapter 3 - Quadratic Functions - 3.2 The Vertex of a Parabola - Exercises and Problems for Section 3.2 - Exercises and Problems - Page 127: 10

$ f(x)=(x+4)^2-13 $ Vertex: $(-4,-13)$ Axis of symmetry: $x=-4$.

The square of half the coefficient of the $x$-term is $\left(\frac{8}{2}\right)^2=16$. Adding and subtracting this number after the $x$-term gives $$ f(x)=x^2+8 x+16-16+3=(x+4)^2-13 $$ The vertex is $(-4,-13)$ and the axis of symmetry is $x=-4$.