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

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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^n2/1+4/1+8/1+16/1+…+2n/1着急打错了…素1/2+1/4+1/8+1/1

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
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

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
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/1
s=1-2n/1=2n/(2n-1)
所以,2/1+4/1+8/1+16/1+…+2n/1=2n/(2n-1)

。。。。写错了?!
2/1???1/2+1/4+1/8+。。。+1/2^n

(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