1/1*3+1/3*5+1/5*7+.1/17*19+1/19*21怎么简便计算?

问题描述:

1/1*3+1/3*5+1/5*7+.1/17*19+1/19*21怎么简便计算?

1/1*3+1/3*5+1/5*7+.1/17*19+1/19*21=【(1-1-3)+(1/3-1/5)+(1/5-1/7)……+(1/17-1/19)+(1/19-1/21)】÷2=【1-1-3+1/3-1/5+1/5-1/7……+1/17-1/19+1/19-1/21】÷2=【1-1/21】÷2=20/21÷2=10/21很高兴为你...