1/n*(n+3)=1/3*(1/n-1/n+3);
1/1*4+1/4*7+1/7*10+..+1/2011*2014
=(1/3)×(1-1/4)+(1/3)×(1/4-1/7)+...+(1/3)×(1/2011-1/2014)
=(1/3)×(1-1/4+1/4-1/7+...+1/2011-1/2014)
=(1/3)×(1-1/2014)
=(1/3)×2013/2014
=671/2014;
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1/n*(n+3)=1/3*(1/n-1/n+3);
1/1*4+1/4*7+1/7*10+..+1/2011*2014
=(1/3)×(1-1/4)+(1/3)×(1/4-1/7)+...+(1/3)×(1/2011-1/2014)
=(1/3)×(1-1/4+1/4-1/7+...+1/2011-1/2014)
=(1/3)×(1-1/2014)
=(1/3)×2013/2014
=671/2014;
很高兴为您解答,skyhunter002为您答疑解惑
如果本题有什么不明白可以追问,