负2分之1减6分之1减12分之1减20分之1减30分之1减42分之1
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负2分之1减6分之1减12分之1减20分之1减30分之1减42分之1
负2分之1减6分之1减12分之1减20分之1减30分之1减42分之1
负2分之1减6分之1减12分之1减20分之1减30分之1减42分之1
1+1/2-1/2-1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7=6/7
1/2-1/6-1/12-1/20-1/30-1/42
=1/2-(1/6+1/12+1/20+1/30+1/42)
=1/2-[1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)+1/(6*7)]
=1/2-(1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7)
=1/2-(1/2-1/7)
=1/2-1/2+1/7
=1/7
1+1/2+1/6+1/12+1/20+/1/30
=1+1/2+1/6+1/12+(1/20+/1/30)
=1+1/2+1/6+1/12+5/60
=1+1/2+1/6+(1/12+1/12)
=1+1/2+(1/6+1/6)
=1+1/2+1/3
=1+5/6
=11/6
1/2-1/6-1/12-1/20-1/30-1/42
=1/2-(1/2-1/3)-(1/3-1/4)-(1/4-1/5)-(1/5-1/6)-(1/6-1/7)
=1/7
(1/3+1/4-2/5)*60=(20/60+15/60-24/60)*60=20+15-24=11
14*(2/7)-3=4-3=1
55*(4/11)=5*4=20
11/12-1/6-5/12=(11-2-5)/12=4/12=1/3
2分之一减6分之一减12分之一减20分之一
1.1/7
2.(1)43
(2)-650
3.1或4023