Question

求 “N的0次方 N的1次方 N的2次方 ...N的n次方” 的求和公式

Answer 1

S=1+N+N^2+N^3+...+N^n

NS = N+N^2+N^3+...+N^n + N^(n+1)

(N-1)S = N^(n+1) - 1

S = (N^(n+1) - 1) / (N-1)