### Home > INT3 > Chapter 3 > Lesson 3.1.1 > Problem3-13

3-13.

For each quadratic function below use the method of completing the square or averaging the $x$‑intercepts to rewrite the equation in graphing form. Then, state the line of symmetry and give the vertex of each parabola. Try to use each method at least once. Homework Help ✎

1. $f ( x ) = x ^ { 2 } + 6 x + 15$

How many ones do you need to make a perfect square? How many do you have?

$f(x)=(x+3)^2+6$
vertex: $(−3,6)$
axis of symmetry: $x=−3$

2. $y = x ^ { 2 } - 4 x + 9$

3. $f ( x ) = x ^ { 2 } - 8 x$

Follow the hints in parts (a) and (b).

4. $y = x ^ { 2 } + 7 x - 2$

$y=(x+3.5)^2−14.25$