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a.
\(M=1.\left[\frac{1}{3}-\frac{1}{5}+.....\frac{1}{97}-\frac{1}{99}\right]\)
\(M=\frac{1}{3}-\frac{1}{99}=\frac{32}{99}\)
b.
\(N=\frac{3}{2}.\left[\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{197}-\frac{1}{199}\right]\)
\(N=\frac{3}{2}.\left[\frac{1}{5}-\frac{1}{199}\right]=\frac{291}{995}\)
mk đầu tiên nha bạn
![](https://rs.olm.vn/images/avt/0.png?1311)
N = ( 3/5 - 3/7 + 3/7 - 3/9 + 3/9 - 3/11 + ... + 3/197 - 3/199 ) : 2
N = ( 3/5 - 3/199 ) : 2
N = 582/995 : 2
N = 291/ 995
![](https://rs.olm.vn/images/avt/0.png?1311)
N=\(3.\left(\frac{1}{5.7}+\frac{1}{7.9}+...+\frac{1}{197.199}\right)\)
N=\(\frac{3}{2}.\left(\frac{2}{5.7}+\frac{2}{7.9}+...+\frac{2}{197.199}\right)\)
N=\(\frac{3}{2}.\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{197}-\frac{1}{199}\right)\)
N=\(\frac{3}{2}.\left(\frac{1}{5}-\frac{1}{999}\right)\)
N=\(\frac{3}{2}.\frac{194}{995}\)
N=\(\frac{291}{995}\)
= 3/5-3/7+3/7-3/9+3/9-3/11+......+3/197-3/199
= 3/5-3/199
= 582/995
![](https://rs.olm.vn/images/avt/0.png?1311)
\(N=\frac{3}{2}\cdot\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+...+\frac{1}{197}-\frac{1}{199}\right)\)
\(N=\frac{3}{2}\cdot\left(\frac{1}{5}-\frac{1}{199}\right)\)
\(N=\frac{3}{2}\cdot\frac{194}{995}\)
\(N=\frac{291}{995}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
BÀi này dễ thôi bạn ạ
N=3(1/5.7+1/7.9+.........+1/197.199)
N=3/2( 1/5-1/7+1/7-1/9+1/9-..........+1/197-1/199)
N=3/2(1/5-1/199)
N=3/2.194/995
N=291/995
k đúng cho mình nhé
N=3.1/2.(1/5-1/7+1/7-1/9+1/9-1/11+...+1/197-1/199)
N=3.1/2.(1/5-1/99)
N=3.1/2.94/495
N=3.47/495
N=47/165
![](https://rs.olm.vn/images/avt/0.png?1311)
N=3/2(1/5-1/7+1/7-1/9+1/9-1/11+...+1/197-1/199)
N=3/2(1/5-1/199)=3/2.194/995=291/995
\(\frac{2}{3}N=\frac{1}{5.7}+\frac{1}{7.9}+\frac{1}{9.11}+...+\frac{1}{197.199}\)
\(=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+...+\frac{1}{197}-\frac{1}{199}\)
\(=\frac{1}{5}-\frac{1}{199}\)
\(=\frac{194}{995}\)
=> \(N=\frac{194}{995}:\frac{2}{3}=\frac{291}{995}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
N=\(\frac{3}{5.7}+\frac{3}{7.9}+............+\frac{3}{197.199}\)
\(=\frac{3}{2}\left(\frac{2}{5.7}+\frac{2}{7.9}+.............+\frac{2}{197.199}\right)\)
\(=\frac{3}{2}\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+............+\frac{1}{197}-\frac{1}{199}\right)\)
\(=\frac{3}{2}.\left(\frac{1}{5}-\frac{1}{199}\right)\)
\(=\frac{3}{2}.\frac{194}{995}\)
\(=\frac{291}{995}\)
N=3/2.(1/5.7+1/7.9+1/9.11+....+1/197.199)
N=3/2.(1/5-1/7+1/7-1/9+1/9-1/11+....+1/197-1/199)
N=3/2.(1/5-1/199)
N=3/2.194/995
N=291/995