①.1/2*5+1/5*8+1/8*11+1/11*14=
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①.1/2*5+1/5*8+1/8*11+1/11*14=
②.1/3*5+1/5*7+1/7*9+1/9*11=
③.3/4+3/28+3/70+3/130=
我会加悬赏分的!
②.1/3*5+1/5*7+1/7*9+1/9*11=
③.3/4+3/28+3/70+3/130=
我会加悬赏分的!
第一题:1/2*5+1/5*8+1/8*11+1/11*14
=1/3×[(1/2 - 1/5)+ (1/5 - 1/8)+ (1/8 - 1/11)+ (1/11 - 1/14)]
=1/3 × (1/2 - 1/14)
=1/3 ×3/7
=1/7
第二题1/3*5+1/5*7+1/7*9+1/9*11
= 1/2×[(1/3 - 1/5)+ (1/5 - 1/7)+ (1/7 - 1/9)+ (1/9 - 1/11)]
=1/2 × (1/3 - 1/11)
=1/2 ×8/33
=4/33
第三题:3/4+3/28+3/70+3/130
=3×[1/(1×4) + 1/(4×7)+1/(7×10)+1/(10×13)]
=1 - 1/13
=12/13
规律:做这类题,要发现数据的特点,采取拆分法
=1/3×[(1/2 - 1/5)+ (1/5 - 1/8)+ (1/8 - 1/11)+ (1/11 - 1/14)]
=1/3 × (1/2 - 1/14)
=1/3 ×3/7
=1/7
第二题1/3*5+1/5*7+1/7*9+1/9*11
= 1/2×[(1/3 - 1/5)+ (1/5 - 1/7)+ (1/7 - 1/9)+ (1/9 - 1/11)]
=1/2 × (1/3 - 1/11)
=1/2 ×8/33
=4/33
第三题:3/4+3/28+3/70+3/130
=3×[1/(1×4) + 1/(4×7)+1/(7×10)+1/(10×13)]
=1 - 1/13
=12/13
规律:做这类题,要发现数据的特点,采取拆分法
①.1/2*5+1/5*8+1/8*11+1/11*14=
1/2*5+1/5*8+1/8*11+1/11*14+.+1/17*20=?
2/5 5/8 8/11 11/14 1 1/17=?
(1/2)*5+(1/5)*8+(1/8)*11+(1/11)*14+(1/14)*17+(1/17)*20
2*5分之1+5*8分之1+8*11分之1+11*14分之一+
5*8/1+8*11/1+11*14/1+14*17/1+17*20/1=?怎样算
1/5*8+1/8*11+1/11*14+1/14*17+1/17*20=?怎样算
1/2 × 1/5 + 1/5 × 1/8 + 1/8 × 1/11 + 1/11 × 1/14 + 1/14 × 1/
(1).11/2*5+11/5*8+11/11*14+11/14*17 (2).1+1/2+3/4+7/8+15/16+
1/2*1/5+1/5*1/8+1/8*1/1+1/11*1/14+1/14*1/17+1/17*1/20的简便算法
简算1/(5*8)+1/(8*11)+1/(11*14)+.+1/(95*98)+1/(98*101)=
1/2*5+1/5*8+1/8*11+1/11*14+1/14*17+1/17*20+1/20*23是多少