三道数学题,快呀11+12-13-14+15+16-17-18+……+99+100(要过程)1+(-2)+3+(-4)+5+(-6)+……+2007+(-2008)(过程) 1-2+3-4+5-6+……-100+101 n(n+2)分之1=
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![三道数学题,快呀11+12-13-14+15+16-17-18+……+99+100(要过程)1+(-2)+3+(-4)+5+(-6)+……+2007+(-2008)(过程) 1-2+3-4+5-6+……-100+101 n(n+2)分之1=](/uploads/image/z/5041592-8-2.jpg?t=%E4%B8%89%E9%81%93%E6%95%B0%E5%AD%A6%E9%A2%98%2C%E5%BF%AB%E5%91%8011%2B12-13-14%2B15%2B16-17-18%2B%E2%80%A6%E2%80%A6%2B99%2B100%EF%BC%88%E8%A6%81%E8%BF%87%E7%A8%8B%EF%BC%891%2B%EF%BC%88-2%EF%BC%89%2B3%2B%28-4%29%2B5%2B%28-6%29%2B%E2%80%A6%E2%80%A6%2B2007%2B%28-2008%29%28%E8%BF%87%E7%A8%8B%EF%BC%89+1-2%2B3-4%2B5-6%2B%E2%80%A6%E2%80%A6-100%2B101+n%28n%2B2%29%E5%88%86%E4%B9%8B1%3D)
三道数学题,快呀11+12-13-14+15+16-17-18+……+99+100(要过程)1+(-2)+3+(-4)+5+(-6)+……+2007+(-2008)(过程) 1-2+3-4+5-6+……-100+101 n(n+2)分之1=
三道数学题,快呀
11+12-13-14+15+16-17-18+……+99+100(要过程)
1+(-2)+3+(-4)+5+(-6)+……+2007+(-2008)(过程)
1-2+3-4+5-6+……-100+101
n(n+2)分之1=
三道数学题,快呀11+12-13-14+15+16-17-18+……+99+100(要过程)1+(-2)+3+(-4)+5+(-6)+……+2007+(-2008)(过程) 1-2+3-4+5-6+……-100+101 n(n+2)分之1=
1、11+12-13-14+15+16-17-18+…+99+100
=11+12+(-13-14+15+16)+(-17-18+19+20)+…+(-97-98+99+100)
=23+(4+4+……+4)
=23+4*22
=111.
2、1+3+5+……+2007+(-2)+(-4)+……(-2008)
= 1004*1+(1004*1003)+1004*(-2)+1004*1003
=-1004
3、1-2+3-4+5-6+…-100+101=(1-2)+(3-4)+...+(99-100)+101=(-1)x50+101= 51
4、1/(n(n+1)(n+2)
=(1/2)*2/n(n+1)(n+2)
=(1/2)*[(n+2)-n]/n(n+1)(n+2)
=(1/2)*[(n+2)/n(n+1)(n+2)-n/n(n+1)(n+2)]
=(1/2)*[1/n(n+1)-1/(n+1)(n+2)]
所以1/1*2*3+……+1/n(n+1)(n+2)
=(1/2)*[1/1*2-1/2*3+……+1/n(n+1)-1/(n+1)(n+2)]
=(1/2)*[1/1*2-1/(n+1)(n+2)]
=(n²+3n)/(4n²+12n+8)
晕,你就顾着快了
连题目也没有
题在哪里^^^^……………………………………
11+12-13-14+15+16-17-18+…+99+100
=11+12+(-13-14+15+16)+(-17-18+19+20)+…+(-97-98+99+100)
=23+(4+4+……+4)
=23+4*22
=111.