数学题1/2+1/6+1/12+1/20+1/30+1/42
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数学题1/2+1/6+1/12+1/20+1/30+1/42
数学题1/2+1/6+1/12+1/20+1/30+1/42
数学题1/2+1/6+1/12+1/20+1/30+1/42
原式=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7
=1-(1/2-1/2)-(1/3-1/3)-(1/4-1/4)-(1/5-1/5)-(1/6-1/6)-1/7
=1-1/7
=6/7
1/2+1/6+1/12+1/20+1/30+1/42
=6/7
1/2+1/6+1/12+1/20+1/30+1/42
=6/7看懂没有?