D=1/6+1/33+1/176+1/336+1/546
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Huhuhu,các bạn giải nhanh giúp mik nha,mik đang cần rất gấp đó ! T^T
Dễ lắm:)
Ta có: \(\frac{1}{176}+\frac{1}{336}+\frac{1}{546}+...+\frac{1}{3416}+\frac{1}{4026}\)
\(=\frac{1}{11.16}+\frac{1}{16.21}+\frac{1}{21.26}+...+\frac{1}{56.61}+\frac{1}{61.66}\)
\(=\frac{1}{5}\cdot\left(\frac{5}{11.16}+\frac{5}{16.21}+\frac{5}{21.26}+...+\frac{5}{56.61}+\frac{5}{61.66}\right)\)
\(=\frac{1}{5}\cdot\left(\frac{1}{11}-\frac{1}{16}+\frac{1}{16}-\frac{1}{21}+\frac{1}{21}-\frac{1}{26}+...+\frac{1}{56}-\frac{1}{61}+\frac{1}{61}-\frac{1}{66}\right)\)
\(=\frac{1}{5}\cdot\left(\frac{1}{11}-\frac{1}{66}\right)\)
\(=\frac{1}{5}\cdot\frac{5}{66}=\frac{1}{66}\)
Giải biểu thức sau:
(1/7+1/91+1/24+1/475).25/24.x+30%=1/2
(1/6+1/66+1/176+1/336+1/546).26/25.x+30%=1/2
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(D=\frac{1}{6}+\frac{1}{66}+\frac{1}{176}+\frac{1}{336}+\frac{1}{546}\)
\(D=\frac{1}{1.6}+\frac{1}{6.11}+\frac{1}{11.16}+\frac{1}{16.21}+\frac{1}{21.26}\)
\(D=\frac{1}{5}\left(\frac{5}{1.6}+\frac{5}{6.11}+\frac{5}{11.16}+\frac{5}{16.21}+\frac{5}{21.26}\right)\)
\(D=\frac{1}{5}\left(\frac{1}{1}-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+...+\frac{1}{21}-\frac{1}{26}\right)\)
\(D=\frac{1}{5}\left(\frac{1}{1}-\frac{1}{26}\right)\)
\(D=\frac{1}{5}.\frac{25}{26}=\frac{5}{26}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
1/6+1/66+1/176+....+1/496.501
=1/1.6+1/6.11+1/11.16+....+1/496.501
=(1/5).(5/1.6+5/6.11+5/11.16+....+5/496.501)
=(1/5).(1-1/6+1/6-1/11+1/11-1/16+...+1/496-1/501)
=(1/5).(1-1/501)
=1/5 . 500/501
=100/501
Ta có: 1/6+1/66+1/176+1/336+...+1/496.501
=1/1.6+1/6.11+1/11.16+1/16.21+...+1/496.501
=1/5.(5/1.6+5/6.11+5/11.16+5/16.21+...+5/496.501)
=1/5.(1-1/6+1/6-1/11+1/11-1/16+1/16-1/21+...+1/496-1/501)
=1/5.(1-1/501)
=1/5.500/501
=100/501
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{5113}{25168}\)
Chúc bạn học tốt !!!