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\(B=\frac{1}{16}+\frac{6}{16.26}+\frac{6}{26.36}+....+\frac{6}{2006.2016}\)
\(=\frac{6}{6.16}+\frac{6}{16.26}+\frac{6}{26.36}+....+\frac{6}{2006.2016}\)
\(=\frac{6}{10}\left(\frac{1}{6}-\frac{1}{16}+\frac{1}{16}-\frac{1}{26}+...+\frac{1}{2006}-\frac{1}{2016}\right)\)
\(=\frac{3}{5}\left(\frac{1}{6}-\frac{1}{2016}\right)\)
\(=\frac{67}{672}\)
\(B=\frac{1}{16}+\frac{6}{16\cdot26}+\frac{6}{26\cdot36}+...+\frac{6}{2006\cdot2016}\)
\(B=\frac{1}{16}+6\left(\frac{1}{16\cdot26}+\frac{1}{26\cdot36}+...+\frac{1}{2006\cdot2016}\right)\)
\(B=\frac{1}{16}+6\left[\frac{1}{10}\left(\frac{10}{16\cdot26}+\frac{10}{26\cdot36}+...+\frac{10}{2006\cdot1016}\right)\right]\)
\(B=\frac{1}{16}+6\left[\frac{1}{10}\left(\frac{1}{16}-\frac{1}{26}+\frac{1}{26}-\frac{1}{36}+...+\frac{1}{2006}-\frac{1}{2016}\right)\right]\)
\(B=\frac{1}{16}+6\left[\frac{1}{10}\left(\frac{1}{16}-\frac{1}{2016}\right)\right]\)
\(B=\frac{1}{16}+6\cdot\left[\frac{1}{10}\cdot\frac{125}{2016}\right]\)
\(B=\frac{1}{16}+6\cdot\frac{26}{4032}\)
\(B=\frac{1}{16}+\frac{25}{672}\)
\(B=\frac{57}{672}\)
\(B=\frac{1}{16}+\frac{6}{16.26}+\frac{6}{26.36}+\frac{6}{36.46}+...+\frac{6}{2006.2016}\) =\(B=\frac{1}{16}+\frac{3}{5}\left(\frac{10}{16.26}+\frac{10}{26.36}+\frac{10}{36.46}+...+\frac{10}{2006.2016}\right)\)
\(B=\frac{1}{16}+\frac{3}{5}\left(\frac{1}{16}-\frac{1}{26}+\frac{1}{26}-\frac{1}{36}+\frac{1}{36}-\frac{1}{46}+...+\frac{1}{2006}-\frac{1}{2016}\right)\)
\(B=\frac{1}{16}+\frac{3}{5}\left(\frac{1}{16}-\frac{1}{2016}\right)\)
đến đây thì ổn rồi
\(A=\frac{16^3.3^{10}+120.6^9}{4^6.3^{12}+6^{11}}\)
\(A=\frac{\left(2^4\right)^3.3^{10}+2^3.3.5.\left(2.3\right)^9}{\left(2^2\right)^6.3^{12}+\left(2.3\right)^{11}}\)
\(A=\frac{2^{12}.3^{10}+2^{12}.3^{10}.5}{2^{12}.3^{12}+2^{11}.3^{11}}\)
\(A=\frac{2^{11}.3^{10}\left(2+2.5\right)}{2^{11}.3^{10}\left(2.3^2+3\right)}\)
\(A=\frac{2+10}{14}\)
\(A=\frac{6}{7}\)
đặt 6/16.26+6.2006.2016=A
ta có:
A=6/16.26+6/26.36+...+6/2006.2016
A=6.(1/16.26+1/26.36+...+1/2006.2016)
A=6(10/16.26+...+10/2006.2016)
A=6(1/16-1/26+1/26-1/36+...+1/2006-1/2016)
A=6(1/17-1/2016)
A=6.1999/34272
A=1999/5712
ta có:
1/16+6/16.26+...+6/2006.2016=1/16+1999/5712=..........
mk nghĩ làm thế này mà ko biết đúng hay sai
đặt A=1/16 + 6/16x26+ 6/26x36 +6/36x46 +......+6/2006x2016
\(\Leftrightarrow A=\frac{1}{16}+\frac{6}{16}-\frac{6}{26}+...+\frac{6}{2006}-\frac{6}{2016}\)
\(\Rightarrow A=\frac{1}{16}+\frac{1}{16}-\frac{1}{26}+...+\frac{1}{2006}-\frac{1}{2016}\)
\(\Rightarrow A=-\frac{1}{2016}\)
hình như là thế
khoảng cách giữa 16 và 26 hình như là 10 thì phải
B= 1/16 + 6/16.26 + 6/26.36 + ... + 6/2006.2016
B= 1/16 + 6( 1/16.26 + 1/26.36 + ... + 1/2006.2016)
10B= 10/16 + 6( 10/16.26 + 10/26.36 + ... + 10/2006.2016)
10B= 10/16 + 6( 1/16 - 1/26 + 1/26 - 1/36 + ... + 1/2006 - 1/2016)
10B= 10/16 + 6( 1/16 - 1/2016)
10B= 10/16 + 6. 125/2016
10B= 10/16 + 125/336
=> B= ( 10/16 + 125/336) : 10
B= 10/16 : 10 + 125/336 :10
B= 1/16 + 25/672 = 67/672
Đây là bài mình tự giải nếu có gì sai thì góp ý nhé