Mean Root

If $r_{1},r_{2}$ , and $r_{3}$ are the roots of the polynomial $5x^3-11x^2+7x-3$ , then the harmonic mean of the roots is $\frac{3}{\frac{1}{r_{1}}+\frac{1}{r_{2}}+\frac{1}{r_{3}}}=\frac{3r_{1}r_{2}r_{3}}{r_{1}r_{2}+r_{1}r_{3}+r_{2}r_{3}}$

By Vieta's formulas , $r_{1}r_{2}r_{3}=\frac{3}{5}$ and $r_{1}r_{2}+r_{1}r_{3}+r_{2}r_{3}=\frac{7}{5}$ . Hence the harmonic mean of the root is $\frac{9}{7}$ . So m + n = 16