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枫下家园 / 望子成龙 / 请教,小孩的数学题--找规律后应用。已知:1-3/(2*4)=(8-3)/(2*4)=5/(2*4) , 1-3/(3×5)=(15-3)/(3*5)=12/(3*5), 如何用在这里?
(1-3/(2*4))*(1-3/(3*5))*(1-3/(4*6)).....*(1-3/(9*11) 因为没法用分数线,我用/代替的。谢谢。
-meetrq66(我住江边);
2009-2-13
{187}
(#5048363@0)
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i guess the rule is 1-x/(y*z ) = (y*z-x)/(y*z)
-c1xwy(洪兴罩俺去战斗);
2009-2-13
(#5048384@0)
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可是如何用它约分,简化运算?
-meetrq66(我住江边);
2009-2-13
(#5048391@0)
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(1-3/(2*4))*(1-3/(3*5))*(1-3/(4*6)).....*(1-3/(9*11)= (2*4-3)/(2*4) * (3*5-3)/(3*5) ... * (9*11-3)/(9*11)
= 5/(2*4) * 12/(3*5) * 21/(4*6) * ... * 96/(9*11)
-canadiantire(轮胎 - Cornelius);
2009-2-13
{109}
(#5048585@0)
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每一项可以用(1-3/(n*(n+2)))=(n-1)/n*(n+3)/(n+2),连乘的时候前后项f分子分母抵消后,剩1/9*12/4=1/3
-phy1204(忍者龟);
2009-2-13
(#5048633@0)
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nth term is: (n)(n+4)/(n+1)(n+3)When you multiply all, you will get (1/4)*[(n+4)/(n+1)]
For your case, n = 8,
So the result is (1/4)*(12/9)=1/3
-bske(Busy Life);
2009-2-13
{113}
(#5048634@0)
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谢谢各位。还要花点时间解释给孩子听。祝各位Happy family day!
-meetrq66(我住江边);
2009-2-13
(#5048826@0)
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这是几年级的题?
-d2park(将山寨进行到底);
2009-2-15
(#5050499@0)
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Sorry,今天才看到你的问题。这个是孩子拿来问我的,大概小学六年级。
-meetrq66(我住江边);
2009-2-18
(#5059048@0)