作业帮1/( )+1/( )+1/( )+1/( )+1/( )+1/( )+1/( )=1,( )里填入7个互不相等且小于20的自然数,使等式成立
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1/( )+1/( )+1/( )+1/( )+1/( )+1/( )+1/( )=1,( )里填入7个互不相等且小于20的自然数,使等式成立
1/( )+1/( )+1/( )+1/( )+1/( )+1/( )+1/( )=1,( )里填入7个互不相等且小于20的自然数,使等式成立
1/( )+1/( )+1/( )+1/( )+1/( )+1/( )+1/( )=1,( )里填入7个互不相等且小于20的自然数,使等式成立
1=1/2+1/2
=1/2+(1/3+1/6)
=1/3+1/6+(1/4+1/12)+(1/9+1/18)
=1/3+1/6+1/5+1/20+1/12+1/9+1/18
∴1/3+1/5+1/6+1/9+1/12+1/18+1/20=1.
(1/3-1/2)/(1/4+1/3)*(1/5-1/4)/(1/6+1/5)*(1/7-1/6)/(1/8+1/7)
=-1/6÷7/12×（-1/20）÷11/30×（-1/42）÷15/56
=-2/7×（-1/20）÷11/30×（-1/42）÷15/56
=-1/70÷11/30×（-1/42）÷15/56
=-3/77×（-1/42）÷15/56
=1/（77×14）÷15/56
=4/1155