1/n*(n+5)=1/5(1/n-1/(n+5))
1/1×6+1/6×11+1/11×16+------+1/101×106
=(1-1/6+1/6-1/11+1/11-1/16+.+1/101-1/106)/5
=(1-1/106)/5
=21/106
1乘6份之一加6乘11份之一加11乘16份之一一直加到101乘106份之一等于几有过程
1/n*(n+5)=1/5(1/n-1/(n+5))
1/1×6+1/6×11+1/11×16+------+1/101×106
=(1-1/6+1/6-1/11+1/11-1/16+.+1/101-1/106)/5
=(1-1/106)/5
=21/106