Algebra

if you move things around you will find this is a quadratic, and you will get x^2 + 7x - 1 = 0 (i believe) and then you can simply plug it in to the quadratic formula

Simplifying gives $x^2 + 7x - 1 = 0$, so the roots are $x = {-7 \pm \sqrt{7^2-4*1*-1} \over 2}$$= {-7 \pm \sqrt{53} \over 2}$. $({{-7 + \sqrt{53}} \over 2}) ^2 + ({{-7 - \sqrt{53}} \over 2})^2 = 51$