答好加150分
问题描述:
答好加150分
1-1/2+1/3-1/4+.+1/99-1/100
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1/(1+101)+1/(2+102)+1/(3+103)+1/(4+104)+.+1/(49+149)+1/(50+150)
答
分子=1-1/2+1/3-1/4+.+1/99-1/100=1+1/3+.+1/99-(1/2+1/4+.+1/100)=1+1/3+.+1/99+(1/2+1/4+.+1/100)-2*(1/2+1/4+.+1/100)=1+1/2+1/3+1/4+.+1/99+1/100-(1+1/2+1/3+.+1/50)令sn=1+1/2+1/3+……+1/n所以分子=s...