Question Number 104775 by MAB last updated on 23/Jul/20
$${let}\:{P}_{{n}} \:{an}\:{n}-{polynomial}. \\ $$$${let}\:{a}_{\mathrm{1}} ,…,{a}_{{n}} \:{its}\:{simple}\:{roots}\: \\ $$$${let}\:{m}_{{k}} \:{the}\:{slope}\:{of}\:{the}\:{tangent}\:{to}\:{P}_{{n}} \:{at} \\ $$$${the}\:{point}\:\left({a}_{{k}} ,\mathrm{0}\right) \\ $$$${prove}\:{that} \\ $$$$\underset{{k}=\mathrm{1}} {\overset{{n}} {\sum}}\frac{\mathrm{1}}{{m}_{{k}} }=\mathrm{0} \\ $$$${what}\:{about}\:{multiple}\:{roots}? \\ $$$$ \\ $$