A=6/3.5 + 6/5.7 +....+ 6/15.17

A= 3(1/3-1/5+1/5-1/7+....+1/15-1/17)

A= 3(1/3-1/17)

A= 3.14/51

A=14/17

Vậy....

A=1/15+1/35+1/63+1/99+1/143+1/195+1/255+1/323

=> A = 1/3.5 + 1/5.7 + 1/7.9 + 1/9.11 + 1/11.13 + 1/13.15 + 1/15.17 + 1/17.19

=> 2A = 1/3 - 1/5 + 1/5 - 1/7 + ..... + 1/17 - 1/19

=> 2A = 1/3 - 1/19

=> 2A = 16/57 => A = 16/57 : 2 = 8/57

=>=> A = 1/3.5 + 1/5.7 + 1/7.9 + 1/9.11 + 1/11.13 + 1/13.15 + 1/15.17 + 1/17.19

=>=> 2A = 1/3 - 1/5 + 1/5 - 1/7 + ..... + 1/17 - 1/19

=> 2A = 1/3 - 1/19

=> 2A = 16/57 => A = 16/57 : 2 = 8/57

1/15+1/35+1/63+1/99+1/143+1/195+1/255+1/323

=1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13+1/13-1/15+1/15-1/17+1/17-1/19

=2/3-2/5+2/5-2/7+2/7-2/9+2/9-2/11+2/11-2/13+2/13-2/15+2/15-2/17+2/17-2/19

=1/3-1/19

2/9

C=1-2/15+1-2/35+1-2/63+...+1-2/195

\(C=6-\left(\dfrac{2}{3x5}+\dfrac{2}{5x7}+\dfrac{2}{7x9}+...+\dfrac{2}{13x15}\right)=\)

\(=6-\left(\dfrac{5-3}{3x5}+\dfrac{7-5}{5x7}+\dfrac{9-7}{7x9}+...+\dfrac{15-13}{13x15}\right)=\)

\(=6-\left(\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{11}+...+\dfrac{1}{13}-\dfrac{1}{15}\right)=\)

\(=6-\left(\dfrac{1}{5}-\dfrac{1}{15}\right)=\dfrac{88}{15}\)

lộn xộn quá cậu viết lại qua kí tự " gõ công thức toán đi"

Mk gõ lại cho

\(\left(\frac{173535}{88375}-\frac{161001}{1365}\right)x3\frac{6}{23}:\left(5-1\frac{187}{253}\right)\)

B = 1/35 + 1/63 + 1/99 + 1/143 + 1/195 + 1/255

   =  1/ 5 x 7 + 1 / 7 x 9 + 1 / 9 x 11 + 1 / 11 x 13 + 1 / 13 x 15 + 1 / 15 x 17

   =  1/5 - 1/7 + 1/ 7 - 1/9 + 1/9 - 1/11 + 1/11 - 1/13 + 1/13 - 1/15 + 1/15 - 1/17

   =  1/5 - 1/17

   =  17/85 -  5/85

   =12/85 

\(B=\frac{6}{85}\)nhé bạn

\(B=\frac{1}{35}+\frac{1}{63}+\frac{1}{99}+\frac{1}{143}+\frac{1}{195}+\frac{1}{255}\)

\(B=\frac{1}{5x7}+\frac{1}{7x9}+\frac{1}{9x11}+\frac{1}{11x13}+\frac{1}{13x15}+\frac{1}{15x17}\)

\(Bx2=\frac{2}{5x7}+\frac{2}{7x9}+\frac{2}{9x11}+\frac{2}{11x13}+\frac{2}{13x15}+\frac{2}{15x17}\)

\(Bx2=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}\)

\(Bx2=\frac{1}{5}-\frac{1}{17}=\frac{12}{85}\)

\(B=\frac{12}{85}:2=\frac{6}{85}\)

Ai trả lời câu hs giúp vs ạ