计算 1/55+2/55+3/55+.+10/55-11/155-12/155-.-20/155
问题描述：
计算 1/55+2/55+3/55+.+10/55-11/155-12/155-.-20/155
答
原式
=(1+2+3+...+10)/55-(11+12+13+...+20)/155
=(1+10)(10/2)/55-(11+20)(10/2)/155
=1-1
=0
答
1/55+2/55+3/55+....+10/55-11/155-12/155-.......-20/155
=1/55*(1+2+3+4+5+6+7+8+9+10-11-12-13-14-15-16-17-18-19-20)
=1/55*(1-11+2-12+3-13+4-14+5-15+6-16+7-17+8-18+9-19+10-20)
=1/55*(-10)*10
=-(100/55)
=-20/11
答
原式=(1+2+3+...+10)/55-(11+12+13+...+20)/155
=(1+10)(10/2)/55-(11+20)(10/2)/155
=1-1
=0
答
45/55-145/155=10/55-10/155=2/11-2/31=40/341