作业帮计算题3道,1.2.3.
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计算题3道,1.2.3.
计算题3道,
1.
2.
3.
计算题3道,1.2.3.
1/(2²-1)+1/(4²-1)+1/(6²-1)+.+1/(100²-1)
=1/[(2-1)(2+1)]+1/[(4-1)(4+1)]+1/[(6-1)(6+1)]+.+1/[(100-1)(100+1)]
=1/(1*3)+1/(3*5)+1/(5*7)+.+1/(99*101)
=[2/(1*3)+2/(3*5)+2/(5*7)+.+2/(99*101)]/2
=[(1-1/3)+(1/3-1/5)+(1/5-1/7)+.+(1/99-1/101)]/2
=(1-1/3+1/3-1/5+1/5-1/7+.+1/99-1/101)/2
=(1-1/101)/2
=(100/101)/2
=50/101
n^2-1=(n+1)(n-1),1/[n^2-1]=0.5*(1/(n-1)-1/(n+1))然后大多数项都约 全化成假分数，答案1 分子分母提出公因式1.1