{"common":{"save":0,"post_id":"7051","level":1,"total":10,"point":10,"point_extra":0},"segment":[{"id":"4854","post_id":"7051","mon_id":"1158924","chapter_id":"1159147","question":"<p>Cho d&atilde;y s\u1ed1&nbsp;<span class=\"math-tex\">$(u_n)$<\/span>&nbsp;\u0111\u01b0\u1ee3c x&aacute;c \u0111\u1ecbnh b\u1edfi&nbsp;<span class=\"math-tex\">$u_1=\\dfrac{1}{3}$<\/span>&nbsp;v&agrave;&nbsp;<span class=\"math-tex\">$u_n=3u_{n-1}$<\/span>&nbsp;,&nbsp;<span class=\"math-tex\">$\\forall n\\ge 2$<\/span>&nbsp;. S\u1ed1 h\u1ea1ng th\u1ee9 n\u0103m c\u1ee7a d&atilde;y s\u1ed1&nbsp;<span class=\"math-tex\">$(u_n)$<\/span>&nbsp;l&agrave;<\/p>","options":["<strong>A.<\/strong> 27","<strong>B.<\/strong> 9","<strong>C.<\/strong> 81","<strong>D.<\/strong> 243"],"correct":"1","level":"1","hint":"","answer":"<p><span class=\"math-tex\">$u_n=3u_{n-1}$<\/span>&nbsp;,&nbsp;<span class=\"math-tex\">$\\forall n\\ge 2$<\/span>&nbsp;&rArr;&nbsp;<span class=\"math-tex\">$q=3$<\/span>&nbsp;&rArr;&nbsp;<span class=\"math-tex\">$u_n=u_1.q^{n-1}=\\dfrac{1}{3}.3^{n-1}=3^{n-2}$<\/span>&nbsp;.<\/p><p>&rArr;&nbsp;<span class=\"math-tex\">$u_5=3^3 = 27$<\/span><\/p><p>Ch\u1ecdn&nbsp; &nbsp;&nbsp;<span style=\"color:#16a085;\"><strong>A.<\/strong> 27.<\/span><\/p>","type":"choose","extra_type":"shape1","user_id":"131","test":"0","date":"2023-12-06 01:43:42","option_type":"txt","len":0},{"id":"4855","post_id":"7051","mon_id":"1158924","chapter_id":"1159147","question":"<p>Cho c\u1ea5p s\u1ed1 nh&acirc;n&nbsp;<span class=\"math-tex\">$(u_n)$<\/span>&nbsp;c&oacute; s\u1ed1 h\u1ea1ng \u0111\u1ea7u&nbsp;<span class=\"math-tex\">$u_1=-2$<\/span>&nbsp;v&agrave;&nbsp;<span class=\"math-tex\">$u_6=486$<\/span>. C&ocirc;ng b\u1ed9i&nbsp;<span class=\"math-tex\">$q$<\/span>&nbsp;b\u1eb1ng<\/p>","options":["<strong>A.<\/strong> <span class=\"math-tex\">$q=3$<\/span>","<strong>B.<\/strong> <span class=\"math-tex\">$q=-3$<\/span>","<strong>C.<\/strong> <span class=\"math-tex\">$q=\\dfrac{1}{3}$<\/span>","<strong>D.<\/strong> <span class=\"math-tex\">$q=-\\dfrac{1}{3}$<\/span>"],"correct":"2","level":"1","hint":"","answer":"<p>Theo \u0111\u1ec1 ta c&oacute;<\/p><p><span class=\"math-tex\">$\\begin{cases}u_1=-2\\\\u_6=486\\end{cases}$<\/span>&nbsp;&hArr;&nbsp;<span class=\"math-tex\">$\\begin{cases}u_1=-2\\\\-2.q^5=486\\end{cases}$<\/span>&nbsp;&nbsp;&rArr;&nbsp;<span class=\"math-tex\">$q^5=-243$<\/span>&nbsp;&rArr;&nbsp;<span class=\"math-tex\">$q=-3$<\/span><\/p><p>Ch\u1ecdn&nbsp; <span style=\"color:#16a085;\">&nbsp;<strong>B.<\/strong>&nbsp;<span class=\"math-tex\">$q=-3$<\/span>&nbsp;.<\/span><\/p>","type":"choose","extra_type":"classic","user_id":"131","test":"0","date":"2023-12-06 01:48:41","option_type":"math","len":0},{"id":"4857","post_id":"7051","mon_id":"1158924","chapter_id":"1159147","question":"<p>Cho c\u1ea5p s\u1ed1 nh&acirc;n&nbsp; 128 ; 64 ; 32 ; 16 ; 8 , c&ocirc;ng b\u1ed9i c\u1ee7a c\u1ea5p s\u1ed1 nh&acirc;n \u0111&oacute; l&agrave;<\/p>","options":["<strong>A.<\/strong> <span class=\"math-tex\">$q=\\dfrac{1}{2}$<\/span>","<strong>B.<\/strong> <span class=\"math-tex\">$q=2$<\/span>","<strong>C.<\/strong> <span class=\"math-tex\">$q=\\sqrt{2}$<\/span>","<strong>D.<\/strong> <span class=\"math-tex\">$q=\\dfrac{1}{\\sqrt{2}}$<\/span>"],"correct":"1","level":"1","hint":"","answer":"<p><span class=\"math-tex\">$u_1=128$<\/span>&nbsp;;&nbsp;<span class=\"math-tex\">$u_2=64$<\/span><\/p><p>V&igrave;&nbsp;<span class=\"math-tex\">$u_2=q.u_1$<\/span>&nbsp;n&ecirc;n&nbsp;<span class=\"math-tex\">$64 = q.128$<\/span>&nbsp;&rArr;&nbsp;<span class=\"math-tex\">$q=\\dfrac{1}{2}$<\/span>&nbsp;.<\/p><p>Ch\u1ecdn&nbsp;<span style=\"color:#16a085;\"> &nbsp;<strong>A.<\/strong>&nbsp;<span class=\"math-tex\">$q=\\dfrac{1}{2}$<\/span>&nbsp;.<\/span><\/p>","type":"choose","extra_type":"classic","user_id":"131","test":"0","date":"2023-12-06 01:52:06","option_type":"math","len":0}]}