2/1+4/1+8/1+16/1+…+2n/1着急打错了…素1/2+1/4+1/8+1/16...+1/2^n
问题描述：
2/1+4/1+8/1+16/1+…+2n/1
着急打错了…素1/2+1/4+1/8+1/16...+1/2^n
答
（1-1\2）+(1\2-1\4)+(1\4-1\8)+(1\8-1\16)+……+(1\n-1\2n)
=1-1\2n (打开括号，合并)
=（2n-1）\2n
答
。。。。写错了？！
2/1？？？1/2+1/4+1/8+。。。+1/2^n
答
令S=2/1+4/1+8/1+16/1+…+2n/1------------1）则2/S=4/1+8/1+16/1+…+2n/1+4n/1--------2)1)式-2)式得2/S=2/1-4n/1s=1-2n/1=2n/(2n-1)所以,2/1+4/1+8/1+16/1+…+2n/1=2n/(2n-1)