(10-7/55×1)+(9-7/55×1)+(8-7/55×1)+.+(1-7/55×1)怎麼簡算?

(10-7/55×1)+(9-7/55×1)+(8-7/55×1)+.+(1-7/55×1)怎麼簡算?

(10-7/55×1)+(9-7/55×1)+(8-7/55×1)+.+(1-7/55×1)
=10/55-7/55+9/55-7/55+8/55-7/55+.1/55-7/55
=【(10+1)×10÷2】/55-7/55*10
=55/55-70/55
=1-14/11
=-3/11