2/1*4+2/4*7+2/7*10+2/10*13+.+2/(3n-2)(3n+1)
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2/1*4+2/4*7+2/7*10+2/10*13+.+2/(3n-2)(3n+1)
2/1*4+2/4*7+2/7*10+2/10*13+.+2/(3n-2)(3n+1)
2/1*4+2/4*7+2/7*10+2/10*13+.+2/(3n-2)(3n+1)
2/(3n-2)(3n+1)=(2/3)*[1/(3n-2)-1/(3n+1)]
所以原式=(2/3)*[1-1/4+1/4-1/7+1/7-1/10+1/10-1/13+.+1/(3n-2)-1/(3n+1)]
=(2/3)*[1-1/(3n+2)]
=(6n+2)/(9n+6)
1,2,4,5,7,8,10,( ),( )
4/15+7/10-1/2=?
2/1*4+2/4*7+2/7*10+2/10*13+.+2/(3n-2)(3n+1)
25.6-2/7-4/7-1/7
2/(1*4)+2/(4*7)+2/(7*10)+2/(10*13)+2/(13*16)+2/(16*19)=?
-8×7/2×(-4/7)×1/4
| 4 1 2 4 | | 1 2 0 2 || 10 5 2 0 || 0 1 1 7 |
1,2,4,7,11,()2,5,10,17,26,()
5+4+3+2+1+8+10+7+18+2
1,1,2,2,4,4,7,7( ),( ) 求( )
1,1,2,2,4,4,7,7( ),( ) 求( )快!
计算题(39*2/7+2/7*4)÷2/7 7/12-(1/4-5/12) 5-3/2*10/21-2/7
1+2+5+4+7+7=
4/3-7/2+4/1+7/2
算24点:4,10,10,2,; 8,2,7,8; 4,7,4,7
(+2又1/10)+(-1 又4/7)+(-2/5)+(-3/7)+(-4 又7/10)用简便方法计算
1,2,4,6,7,10,10,(),()找规律
1 2 4 6 7 10 10规律是什么