更新时间2018-10-21 16:22:29
求步骤,详细一点
设S=1/2+1/2²+......+1/(2^n)
两边同时乘以1/2得:1/2·S=1/2²+......+1/(2^n)+1/[2^(n+1)]
故:S-1/2·S=(1/2+1/2²+......+1/(2^n))-{1/2²+......+1/(2^n)+1/[2^(n+1)]}
故:1/2·S=1/2-1/[2^(n+1)]
故:S=1-1/(2^n)
即;1/2+1/2²+......+1/(2^n)=1-1/(2^n)