分母两个数相乘都是差为5
所以原式=(1/5)×(1-1/6+1/6-1/11+1/11-1/16……+1/2006-1/2011)
=(1/5)×(1-1/2011)
=(1/5)×(2010/2011)
=402/2011
祝你开心