(10-2/55*1)+(9-2/55*2)+(8-2/55*3)+...+(1-2/55*10)=

问题描述:

(10-2/55*1)+(9-2/55*2)+(8-2/55*3)+...+(1-2/55*10)=

(10-2/55*1)+(9-2/55*2)+(8-2/55*3)+...+(1-2/55*10)
= (10+9+8+…+1)-2/55*(1+2+3+…10)
= (1-2/55)*(1+2+3+…10)
=53/55*55
=53