如题,
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如题,如题,如题,110/30+110/42+110/56+110/72+110/90+110/110=110(1/30+1/42+1/56+1/72+1/90+1/110)=110[1/(5×6)+
如题,
如题,
如题,
110/30+110/42+110/56+110/72+110/90+110/110
=110(1/30+1/42+1/56+1/72+1/90+1/110)
=110[1/(5×6)+1/(6×7)+1/(7×8)+1/(8×9)+1/(9×10)+1/(10×11)]
=110(1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11)
=110(1/5-1/11)
=110(11/55-5/55)
=110×(6/55)
=12
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少了+110/72
=110×(1/5×6+1/6×7+1/7×8+1/8×9+1/9×10+1/10×11)
=110×(1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11)
=110×)1/5-1/11)
=12没有110/72，有还用找你吗..=110×(1/5×6+1/6×7+1/7×8+1/9×10+1/1...
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少了+110/72
=110×(1/5×6+1/6×7+1/7×8+1/8×9+1/9×10+1/10×11)
=110×(1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11)
=110×)1/5-1/11)
=12
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典型的裂项求解，1/5*1/6=1/5-1/6