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

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

Có N = 3 . (1/5 .  7 + 1/7 . 9 + .... + 1/197 . 199)

    2N =  3 . (2/5 . 7 + 2/7 . 9 + ... + 2/197 . 199)

    2N = 3 . (1/5 - 1/7 + 1/7 - 1/9 + ... + 1/197 - 1/199)

    2N = 3 . (1/5 - 1/199)

      N = \(\frac{3.\left(\frac{1}{5}-\frac{1}{199}\right)}{2}\)

      N = (3 . 194/995) : 2

Bạn tự tính nốt nhé chúc bạn học tốt

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

N=3/5.7+3/7.9+........+3/197.199

=>N=3/2(2/5.7+2/7.9+.....+2/197.199)

=>N=3/2(1/5-1/7+1/7-1/9+........+1/197-1/199)

=>N=3/2(1/5-1/199)

=>N=3/2x194/995=291/995

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

nguyen van nam, bạn có thể ghi rõ hơn không ?

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

\(N=\frac{3}{2}\cdot\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+...+\frac{1}{197}-\frac{1}{199}\right)\)

\(N=\frac{3}{2}\cdot\left(\frac{1}{5}-\frac{1}{199}\right)\)

\(N=\frac{3}{2}\cdot\frac{194}{995}\)

\(N=\frac{291}{995}\)

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

\(\frac{2}{3}N=\frac{1}{5.7}+\frac{1}{7.9}+\frac{1}{9.11}+...+\frac{1}{197.199}\)

          \(=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+...+\frac{1}{197}-\frac{1}{199}\)

          \(=\frac{1}{5}-\frac{1}{199}\) 

          \(=\frac{194}{995}\)

=> \(N=\frac{194}{995}:\frac{2}{3}=\frac{291}{995}\)

=> 2N = 2.3/5.7 + 2.3/7.9 + 2.3/9.11 + ... + 2.3/197.199

=> 2N = 3. (1/5 - 1/7 + 1/7 - 1/9 + 1/9 - 1/11   + ... + 1/197 - 1/199

=> 2N = 3. (1/5 - 1/199) = 3. 194/995 = 582/995

=> N = 582/995 : 2 = 291/995

Tinh bang mt do nha.

P = 1 - 1/2 + 1/2 - 1/4 + 1/4 - 1/7 + ... + 1/46 - 1/56

P = 1 - 1/56

P = 55/56