What constant should you add to the expression $x^2+6x$ to form a perfect square trinomial?

Solve $x^2+6x+5$ for $x$ by completing the square.

Solve $x^2+\frac{7}{2}x-3=0$ by completing the square. Give the exact roots in the simplest radical form.

A ball's height, in units of feet, is given by: $h\left(t\right)=-16t^2+64t+80$, where $t$ is in units of seconds. Use completing the square to find the time when the ball reaches its maximum height.

Which statement best explains why using the completing the square method is the preferred strategy over using factoring and the quadratic formula?