1+x+x^2+...+x^99 = (x^100 -1)/(x-1)
(x-1)(1+x+x^2+...+x^99) = x^100 -1
﹙﹣2﹚∧50＋﹙﹣2﹚∧49＋···＋﹙﹣2﹚＋1
=[1- (-2)^51]/(1+2)
=(1/3)[ 1-(-2)^51]