1-3 5-7 9-11 97-99 101等于多少
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79×99-79=79*(99-1)=79*98=79*(100-2)=79*100-79*2=7900-158=7742
79*99+79=79(99+1)=7900
1/15+1/35+1/63+1/99=(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11)÷2=(1/3-1/11)÷2=4/33
79+99+79=(79+1)+(99⑵)+(79+1)=80+97+80=257查看原帖
1/15+1/35+1/63+1/99+1/143=[1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13]/2=[1/3-1/13]/2=5/39
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恩,是裂项法1/3=1/1*3=(1/3-1/5)/2,1/15=1/3*5=(1/3-1/5)/2,1/35=1/5*7=(1/5-1/7)/2,1/63=1/7*9=(1/7-1/9)/2,1/9
分母是两个数相乘吧?1/(1×3)=(1-1/3)÷21/(3×5)=(1/3-1/5)÷2.1/(2001×2003)=(1/2001-1/2003)÷2原式=(1-1/3+1/3-1/5+...+
1/35+1/63+1/99+1/143=1/(5×7)+1/(7×9)+1/(9×11)+1/(11×13)=1/2×(1/5-1/7)+1/2×(1/7-1/9)+1/2×(1/9-1/11)+1
原式=79×(99+1)=79×100=7900
16乘125=2×8×125=2×1000=200048乘99=48×100-48=4800-48=475247乘101=4700+47=474758乘17+17乘42=(58+42)×17=100×
79×(99+98/79)+1=79×(100+19/79)+1=79×100+79×19/79+1=7900+19+1=7920
64×79+35×79+79=(64+35+1)×79=100×79=7900估计题目中的79错打成39了.
1求采纳!
1/35+1/63+1/99+1/143=1/(5*7)+1/(7*9)+1/(9*11)+1/(11*13)=(1/2)*[(1/5)-(1/7)]+(1/2)*[(1/7)-(1/9)]+(1/2
254再问:过程再问:过程再答:
79²+79*21=79x(79+21)=79x100=79002、65²-35²=(65+35)(65-35)=100x30=30003、99²+2*99+1
1/15+1/35+1/63+1/99=1/3*5+1/5*7+1/7*9+1/9*11=(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11)*1/2=(1/3-1/11)*1/2=4
1/3+1/15+1/35+1/63+1/99=[(1-1/3)+(1/3-1/5)+(1/5-1/7)+(1/7-1/9)+(1/9-1/11)]÷(3-1)=[1-1/3+1/3-1/5+1/5-