Chú ý: Để đảm bảo quyền lợi và bảo vệ tài khoản của mình
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{"common":{"save":0,"post_id":"7789","level":3,"total":10,"point":10,"point_extra":0},"segment":[{"id":"7358","post_id":"7789","mon_id":"1159278","chapter_id":"1159282","question":"<p>V\u1edbi a, b b\u1ea5t k\u1ef3. Ch\u1ecdn kh\u1eb3ng \u0111\u1ecbnh <strong>sai<\/strong>.<\/p>","options":["<strong>A.<\/strong> <span class=\"math-tex\">$a^2+3>-2a$<\/span>","<strong>B.<\/strong> <span class=\"math-tex\">$4a+4\\le a^2+8$<\/span>","<strong>C.<\/strong> <span class=\"math-tex\">$a^2+1<-a$<\/span>","<strong>D.<\/strong> <span class=\"math-tex\">$-ab-b^2\\le a^2$<\/span>"],"correct":"3","level":"3","hint":"","answer":"<p>Câu sai là <span style=\"color:#16a085;\"><strong>C.<\/strong> <span class=\"math-tex\">$a^2+1<-a$<\/span>.<\/span><\/p><p><strong>A.<\/strong> <span class=\"math-tex\">$a^2+3>-2a$<\/span> hay <span class=\"math-tex\">$a^2+2a+3>0$<\/span> hay <span class=\"math-tex\">$(a+1)^2+2>0$<\/span> (\u0111úng).<\/p><p><strong>B.<\/strong> <span class=\"math-tex\">$4a+4\\le a^2+8$<\/span> hay <span class=\"math-tex\">$a^2-4a+4\\ge0$<\/span> hay <span class=\"math-tex\">$(a-2)^2\\ge0$<\/span> (\u0111úng).<\/p><p><strong>C.<\/strong> <span class=\"math-tex\">$a^2+1<-a$<\/span> hay <span class=\"math-tex\">$a^2+a+1<0$<\/span> hay <span class=\"math-tex\">$\\bigg(a+\\dfrac{1}{2}\\bigg)^2+\\dfrac{3}{4}<0$<\/span> (<span style=\"color:#c0392b;\">sai<\/span>).<\/p><p><strong>D.<\/strong> <span class=\"math-tex\">$-ab-b^2\\le a^2$<\/span> hay <span class=\"math-tex\">$a^2+ab+b^2\\ge0$<\/span> hay <span class=\"math-tex\">$\\bigg(a+\\dfrac{b}{2}\\bigg)^2+\\dfrac{3b^2}{4}\\ge0$<\/span> (\u0111úng).<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"127","test":"0","date":"2024-10-06 09:25:39","option_type":"math","len":0},{"id":"7360","post_id":"7789","mon_id":"1159278","chapter_id":"1159282","question":"<p>Cho x + y > 1. Ch\u1ecdn kh\u1eb3ng \u0111\u1ecbnh \u0111úng.<\/p>","options":["<strong>A.<\/strong> <span class=\"math-tex\">$x^2+y^2>\\dfrac{1}{2}$<\/span>","<strong>B.<\/strong> <span class=\"math-tex\">$x^2+y^2<\\dfrac{1}{2}$<\/span>","<strong>C.<\/strong> <span class=\"math-tex\">$x^2+y^2=\\dfrac{1}{2}$<\/span>","<strong>D.<\/strong> <span class=\"math-tex\">$x^2+y^2\\le\\dfrac{1}{2}$<\/span>"],"correct":"1","level":"3","hint":"","answer":"<p>Ch\u1ecdn <span style=\"color:#16a085;\"><strong>A.<\/strong> <span class=\"math-tex\">$x^2+y^2>\\dfrac{1}{2}$<\/span>.<\/span><\/p><p>T\u1eeb x + y > 1, bình ph\u01b0\u01a1ng hai v\u1ebf (hai v\u1ebf \u0111\u1ec1u d\u01b0\u01a1ng) \u0111\u01b0\u1ee3c <span class=\"math-tex\">$(x+y)^2>1$<\/span> hay <span class=\"math-tex\">$x^2+2xy+y^2>1$<\/span> (1).<\/p><p>T\u1eeb <span class=\"math-tex\">$(x-y)^2\\ge0$<\/span> suy ra <span class=\"math-tex\">$x^2-2xy+y^2\\ge0$<\/span> (2).<\/p><p>C\u1ed9ng t\u1eebng v\u1ebf (1) v\u1edbi (2) \u0111\u01b0\u1ee3c <span class=\"math-tex\">$2x^2+2y^2>1$<\/span>.<\/p><p>Chia hai v\u1ebf cho 2 ta \u0111\u01b0\u1ee3c <span style=\"color:#16a085;\"><span class=\"math-tex\">$x^2+y^2>\\dfrac{1}{2}$<\/span>.<\/span><\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"127","test":"0","date":"2024-10-06 09:32:11","option_type":"math","len":0},{"id":"7361","post_id":"7789","mon_id":"1159278","chapter_id":"1159282","question":"<p>M\u1ed9t tam giác có \u0111\u1ed9 dài các c\u1ea1nh là 3, x, 6 (x là s\u1ed1 nguyên). Khi \u0111ó:<\/p>","options":["<strong>A.<\/strong> 10","<strong>B.<\/strong> 4","<strong>C.<\/strong> 1","<strong>D.<\/strong> 11"],"correct":"2","level":"3","hint":"","answer":"<p>Ch\u1ecdn <span style=\"color:#16a085;\"><strong>B.<\/strong> 4.<\/span><\/p><p>Áp d\u1ee5ng b\u1ea5t \u0111\u1eb3ng th\u1ee9c tam giác ta có 6 – 3 < x < 3 + 6 hay 3 < x < 9.<\/p><p>Mà x ∈ Z nên x ∈ {4 ; 5 ; 6 ; 7 ; 8}.<\/p>","type":"choose","extra_type":"classic","time":"0","user_id":"127","test":"0","date":"2024-10-06 09:35:46","option_type":"txt","len":0}]}