Chú ý: Để đảm bảo quyền lợi và bảo vệ tài khoản của mình
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{"common":{"save":0,"post_id":"6703","level":2,"total":10,"point":10,"point_extra":0},"segment":[{"id":"7282","mon_id":"1158767","chapter_id":"1158999","post_id":"6703","question":"<p>Tìm t\u1eadp nghi\u1ec7m c\u1ee7a b\u1ea5t ph\u01b0\u01a1ng trình <span class=\"math-tex\">$-x^2-3x-4<0$<\/span>.<\/p>","options":["<strong>A.<\/strong> <span class=\"math-tex\">$S=(-\\infty;-4)\\cup(-1;+\\infty)$<\/span>","<strong>B.<\/strong> <span class=\"math-tex\">$S=(-\\infty;-1)\\cup(4;+\\infty)$<\/span>","<strong>C.<\/strong> <span class=\"math-tex\">$S=(-4;-1)$<\/span>","<strong>D.<\/strong> <span class=\"math-tex\">$S=\\mathbb{R}$<\/span>"],"correct":"4","level":"2","hint":"","answer":"<p>Xét tam th\u1ee9c b\u1eadc hai <span class=\"math-tex\">$-x^2-3x-4<0$<\/span> có h\u1ec7 s\u1ed1 <span class=\"math-tex\">$a=-1<0$<\/span> và <span class=\"math-tex\">$\\Delta=(-3)^2-4.(-1).(-4)=-7<0$<\/span><\/p><p>nên <span class=\"math-tex\">$-x^2-3x-4<0$<\/span>, <span class=\"math-tex\">$\\forall x\\in\\mathbb{R}$<\/span>.<\/p><p>Do \u0111ó t\u1eadp nghi\u1ec7m c\u1ee7a b\u1ea5t ph\u01b0\u01a1ng trình <span class=\"math-tex\">$-x^2-3x-4<0$<\/span> là <span style=\"color:#16a085;\"><span class=\"math-tex\">$S=\\mathbb{R}$<\/span><\/span><\/p><p>Ch\u1ecdn <span style=\"color:#16a085;\"><strong>D.<\/strong> <span class=\"math-tex\">$S=\\mathbb{R}$<\/span><\/span><\/p>","type":"choose","extra_type":"classic","user_id":"131","test":"0","date":"2023-09-21 00:47:25","option_type":"math","len":0},{"id":"7285","mon_id":"1158767","chapter_id":"1158999","post_id":"6703","question":"<p>Giá tr\u1ecb c\u1ee7a m \u0111\u1ec3 tam th\u1ee9c <span class=\"math-tex\">$f(x)=x^2-(m+2)x+8m+1$<\/span> \u0111\u1ed5i d\u1ea5u hai l\u1ea7n là:<\/p>","options":["<strong>A.<\/strong> <span class=\"math-tex\">$m\\le0$<\/span> ho\u1eb7c <span class=\"math-tex\">$m\\ge28$<\/span>","<strong>B.<\/strong> m < 0 ho\u1eb7c m > 28","<strong>C.<\/strong> m > 0","<strong>D.<\/strong> 0 < m < 28"],"correct":"2","level":"2","hint":"","answer":"<p>Ta có: <span class=\"math-tex\">$f(x)=x^2-(m+2)x+8m+1$<\/span> là m\u1ed9t tam th\u1ee9c b\u1eadc hai.<\/p><p>\u0110\u1ec3 f(x) \u0111\u1ed5i d\u1ea5u 2 l\u1ea7n thì f(x) có <\/p><p><span class=\"math-tex\">$\\Delta >0 \\Leftrightarrow$<\/span> <span class=\"math-tex\">$(m+2)^2-4(8m+1)>0$<\/span> <\/p><p> <span class=\"math-tex\">$ \\Leftrightarrow m^2-28m>0 $<\/span> <\/p><p> <span class=\"math-tex\">$\\Leftrightarrow m<0$<\/span> ho\u1eb7c m > 28<\/p><p>Ch\u1ecdn <span style=\"color:#16a085;\"><strong>B.<\/strong> m < 0 ho\u1eb7c m > 28<\/span><\/p>","type":"choose","extra_type":"classic","user_id":"131","test":"0","date":"2023-09-21 00:53:17","option_type":"math","len":0},{"id":"7286","mon_id":"1158767","chapter_id":"1158999","post_id":"6703","question":"<p>T\u1eadp xác \u0111\u1ecbnh c\u1ee7a hàm s\u1ed1 <span class=\"math-tex\">$f(x)=\\sqrt{x+1}+\\dfrac{1}{x}$<\/span> là:<\/p>","options":["<strong>A. <\/strong><span class=\"math-tex\">$D=[1;+\\infty)$<\/span>","<strong>B. <\/strong><span class=\"math-tex\">$D=\\mathbb{R}\\setminus \\{-1;0\\}$<\/span>","<strong>C. <\/strong><span class=\"math-tex\">$D=[-1;+\\infty)\\setminus\\{0\\}$<\/span>","<strong>D. <\/strong><span class=\"math-tex\">$D=\\mathbb{R}\\setminus \\{0\\}$<\/span>"],"correct":"3","level":"2","hint":"","answer":"<p>Hàm s\u1ed1 xác \u0111\u1ecbnh khi <span class=\"math-tex\">$\\begin{cases}x+1\\ge0\\\\x\\ne0\\end{cases}$<\/span> <span class=\"math-tex\">$\\Leftrightarrow \\begin{cases}x\\ge-1\\\\x\\ne0\\end{cases}$<\/span> <span class=\"math-tex\">$\\Leftrightarrow x\\in[-1;+\\infty)\\setminus\\{0\\}$<\/span><\/p><p>Ch\u1ecdn <span style=\"color:#16a085;\"><strong>C. <\/strong><span class=\"math-tex\">$D=[-1;+\\infty)\\setminus\\{0\\}$<\/span><\/span><\/p>","type":"choose","extra_type":"classic","user_id":"131","test":"0","date":"2023-09-21 01:00:56","option_type":"math","len":0}]}