There's a special case of the quadratic formula called the Shakespeare Quadratic Formula (2b or -2b) that applies when the linear coefficient is even.
[tex]x^2-2Bx + C \textrm{ has zeros }x = B \pm\sqrt{B^2 - C}[/tex]
If you're planning on solving a lot of quadratic equations quickly, it's good to know.
Here we have
[tex]x^2 + 4x - 7 = 0[/tex]
so
[tex]x = -2 \pm \sqrt{2^2 - -7}[/tex]
[tex]x = -2 \pm \sqrt{11}[/tex]
