If two roots of $20x^3-16x^2+x+1=0$  are equal then the roots are

Sum = $\frac{4}{5}$  product =$\frac{-1}{20}$  (by verification equal roots of the given equation  are $\frac{1}{2},\frac{1}{2},\frac{-1}{5}$ , since $s_1=\frac{1}{2}+\frac{1}{2}-\frac{1}{5}=\frac{4}{5}and s_3=\frac{1}{2}·\frac{1}{2}·-\frac{1}{5}=\frac{-1}{20}$)