Let x1,x2,…,x2016 be the roots of x2016+x2015+⋯+x+1=0.Find (1−x1)21+(1−x2)21+⋯+(1−x2016)21.
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Let y=1−x1. Solving for x in terms of y, we find x=yy−1.Then (yy−1)2016+(yy−1)2015+⋯+(yy−1)+1=0.Hence, (y−1)2016+y(y−1)2015+y2(y−1)2014+⋯+y2015(y−1)+y2016=0.This expands as (y2016−2016y2015+(22016)y2014−⋯)+y(y2015−2015y2014+(22015)y2013−⋯)+y2(y2014−2014y2013+(22014)y2012−⋯)+⋯+y2015(y−1)+y2016=0.The coefficient of y2016 is 2017. The coefficient of y2015 is −2016−2015−⋯−2−1=−22016⋅2017=−2033136.The coefficient of y2014 is (22016)+(22015)+⋯+(22).By the Hockey Stick Identity, (22016)+(22015)+⋯+(22)=(32017)=1365589680.The roots of the polynomial in y above are yk=1−xk1 for 1≤k≤2016, so by Vieta's formulas, y1+y2+⋯+y2016=20172033136=1008,and y1y2+y1y3+⋯+y2015y2016=20171365589680=677040.Therefore, (1−x1)21+(1−x2)21+⋯+(1−x2016)21=y12+y22+⋯+y20162=(y1+y2+⋯+y2016)2−2(y1y2+y1y3+⋯+y2015y2016)=10082−2⋅677040=−338016.