原式=(1+1/2)-(3-1/6)+(3+1/12)-(5-1/20)+(5+1/30)-(7-1/42)+(7+1/56)-(9-1/72)+(9+1/90)
=1+1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90
=1+1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10
=2-1/10
=19/10
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启航新课堂有理数的加减混合运算(第一课时)能力拓展演练和第十题的第七小题