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(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
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