<s>[INST] Quadratic equation formula help / simplification I have this quadratic equation, 
$ x^{2} + \frac{10}{3}x -\frac{80}{3} = 0 $
I use the quadratic formula to solve and simplify 
$-10 \pm \frac{\sqrt{100-(4)(3)(-80)}}{6}$ = $ \frac{-10 \pm \sqrt{1060}}{6}$
my book says it should simplify to 
$ \frac{1}{3} ( -5 \pm \sqrt{73}) $
but i cant get this simplification can anyone show me if they can? Thank you. 
 [/INST] Your solution seems correct, indeed
$$x^{2} + \frac{10}{3}x -\frac{80}{3} = 0\iff3x^2+10x-80=0$$
$$ \frac{-10 \pm\sqrt{100-(4)(3)(-80)}}{6}=-\frac53\pm\frac{\sqrt{265}}{3}$$
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