{"segment":[{"part":[{"title":"\u0110i\u1ec1n d\u1ea5u th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["<"]]],"list":[{"point":10,"width":50,"content":"","type_input":"","ques":"<span class='basic_left'>Gi\u1ea3 s\u1eed $a < b$, h\u00e3y so s\u00e1nh: $2a + 5$ v\u00e0 $2b + 5$<br\/><b>\u0110\u00e1p \u00e1n:<\/b> $2a + 5$ _input_ $2b + 5$<\/span>","hint":"Khi c\u1ed9ng c\u00f9ng m\u1ed9t s\u1ed1 v\u00e0o c\u1ea3 hai v\u1ebf c\u1ee7a m\u1ed9t b\u1ea5t \u0111\u1eb3ng th\u1ee9c ta \u0111\u01b0\u1ee3c b\u1ea5t \u0111\u1eb3ng th\u1ee9c m\u1edbi c\u00f9ng chi\u1ec1u v\u1edbi b\u1ea5t \u0111\u1eb3ng th\u1ee9c \u0111\u00e3 cho","explain":"<span class='basic_left'>Ta c\u00f3:<br\/>$a < b$ $\\Rightarrow 2a < 2b \\Rightarrow 2a + 5 < 2b + 5 $<br\/>V\u1eady d\u1ea5u c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 <span class='basic_pink'>\"<\"<\/span><\/span>"}],"id_ques":1251},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":10,"ques":"S\u1ed1 $a$ l\u00e0 s\u1ed1 \u00e2m hay s\u1ed1 d\u01b0\u01a1ng n\u1ebfu: $15a + 1 < 18a + 1$","select":[" A. S\u1ed1 d\u01b0\u01a1ng"," B. S\u1ed1 \u00e2m"],"hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>+ Khi nh\u00e2n c\u1ea3 hai v\u1ebf c\u1ee7a b\u1ea5t \u0111\u1eb3ng th\u1ee9c v\u1edbi c\u00f9ng m\u1ed9t s\u1ed1 d\u01b0\u01a1ng ta \u0111\u01b0\u1ee3c b\u1ea5t \u0111\u1eb3ng th\u1ee9c m\u1edbi c\u00f9ng chi\u1ec1u v\u1edbi b\u1eaft \u0111\u1eb3ng th\u1ee9c \u0111\u00e3 cho<br\/>+ Khi nh\u00e2n c\u1ea3 hai v\u1ebf c\u1ee7a b\u1ea5t \u0111\u1eb3ng th\u1ee9c v\u1edbi c\u00f9ng m\u1ed9t s\u1ed1 \u00e2m ta \u0111\u01b0\u1ee3c b\u1ea5t \u0111\u1eb3ng th\u1ee9c m\u1edbi ng\u01b0\u1ee3c chi\u1ec1u v\u1edbi b\u1eaft \u0111\u1eb3ng th\u1ee9c \u0111\u00e3 cho<\/span> <br\/><br\/><span class='basic_left'><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/>Ta c\u00f3: $15a + 1 < 18a + 1$<br\/>$\\Rightarrow 15a + 1 + (-1) < 18a + 1 + (-1) \\\\ \\Rightarrow 15a < 18a$<br\/>M\u00e0 $15 < 18$<br\/>$ \\Rightarrow a > 0$ hay $a$ l\u00e0 s\u1ed1 d\u01b0\u01a1ng<br\/>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 <span class='basic_pink'>A. S\u1ed1 d\u01b0\u01a1ng<\/span>","column":2}],"id_ques":1252},{"title":"\u0110i\u1ec1n d\u1ea5u v\u00e0 s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["<"],["-6"]]],"list":[{"point":10,"width":50,"content":"","type_input":"","ques":"Gi\u1ea3i b\u1ea5t ph\u01b0\u01a1ng tr\u00ecnh: $-5x + 6 > 30 - x$<br\/><b>\u0110\u00e1p \u00e1n:<\/b> $x$ _input_ _input_","hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>- Khi chuy\u1ec3n m\u1ed9t h\u1ea1ng t\u1eed c\u1ee7a b\u1ea5t ph\u01b0\u01a1ng tr\u00ecnh t\u1eeb v\u1ebf n\u00e0y sang v\u1ebf kia ta ph\u1ea3i \u0111\u1ed5i d\u1ea5u h\u1ea1ng t\u1eed \u0111\u00f3<br\/>- Khi nh\u00e2n hai v\u1ebf c\u1ee7a b\u1ea5t ph\u01b0\u01a1ng tr\u00ecnh v\u1edbi c\u00f9ng m\u1ed9t s\u1ed1 kh\u00e1c $0$, ta ph\u1ea3i:<br\/>+ Gi\u1eef nguy\u00ean chi\u1ec1u b\u1ea5t ph\u01b0\u01a1ng tr\u00ecnh n\u1ebfu s\u1ed1 \u0111\u00f3 d\u01b0\u01a1ng<br\/>+ \u0110\u1ed5i chi\u1ec1u b\u1ea5t ph\u01b0\u01a1ng tr\u00ecnh n\u1ebfu s\u1ed1 \u0111\u00f3 \u00e2m<\/span> <br\/><span class='basic_left'><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/>Ta c\u00f3:<br\/>$-5x + 6 > 30 - x$ <br\/> $\\Leftrightarrow -5x + x > 30 - 6$ <br\/>$\\Leftrightarrow -4x > 24 $<br\/>$\\Leftrightarrow x < 24 : (-4) $<br\/>$\\Leftrightarrow x < -6 $<br\/>V\u1eady t\u1eadp nghi\u1ec7m c\u1ee7a b\u1ea5t ph\u01b0\u01a1ng tr\u00ecnh l\u00e0 $\\left\\{x \\mid x < -6\\right\\}$<br\/>D\u1ea5u v\u00e0 s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u1ea7n l\u01b0\u1ee3t l\u00e0 <span class='basic_pink'>\"<\"; $-6$<\/span>"}],"id_ques":1253},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":10,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai29/lv3/img\/3.jpg' \/><\/center><br\/>Gi\u1ea3i b\u1ea5t ph\u01b0\u01a1ng tr\u00ecnh $2(x + 4) > 10x - (3x + 17)$","select":[" A. $\\left\\{x \\mid x > -5\\right\\}$"," B. $\\left\\{x \\mid x < -5\\right\\}$","C. $\\left\\{x \\mid x < 5 \\right\\}$","D. $\\left\\{x \\mid x > 5 \\right\\}$"],"hint":"S\u1eed d\u1ee5ng quy t\u1eafc chuy\u1ec3n v\u1ebf v\u00e0 quy t\u1eafc nh\u00e2n ho\u1eb7c quy t\u1eafc chia v\u1edbi m\u1ed9t s\u1ed1 \u0111\u1ec3 gi\u1ea3i.","explain":"<span class='basic_left'>Ta c\u00f3 $2(x + 4) > 10x - (3x + 17)$<br\/>$\\Leftrightarrow 2x + 8 > 10x - 3x - 17$<br\/>$\\Leftrightarrow 2x + 8 > 7x - 17$<br\/>$\\Leftrightarrow 7x - 2x < 8 + 17$ <br\/>$\\Leftrightarrow 5x < 25$<br\/>$\\Leftrightarrow x < 25 : 5$<br\/>$\\Leftrightarrow x < 5$<br\/>V\u1eady t\u1eadp nghi\u1ec7m c\u1ee7a b\u1ea5t ph\u01b0\u01a1ng tr\u00ecnh l\u00e0 $\\left\\{x \\mid x < 5\\right\\}$ <br\/>\u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 <span class='basic_pink'>C. $\\left\\{x \\mid x < 5\\right\\}$<\/span><\/span>","column":2}],"id_ques":1254},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":10,"ques":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai29/lv3/img\/5.jpg' \/><\/center> T\u00ecm c\u00e1c nghi\u1ec7m nguy\u00ean d\u01b0\u01a1ng c\u1ee7a b\u1ea5t ph\u01b0\u01a1ng tr\u00ecnh: $18 - 2x \\geq 0$<\/span>","select":[" A. $x \\in \\left\\{1; 2; 3; 4; 5 ; 6\\right\\}$"," B. $x \\in \\left\\{ 2; 3; 4; 5; 6; 7; 8\\right\\}$","C. $x \\in \\left\\{0; 1; 2; 3; 4; 5; 6; 7; 8\\right\\}$","D. $x \\in \\left\\{ 1; 2; 3; 4; 5; 6; 7; 8; 9\\right\\}$"],"hint":"S\u1eed d\u1ee5ng quy t\u1eafc chuy\u1ec3n v\u1ebf v\u00e0 quy t\u1eafc nh\u00e2n v\u1edbi m\u1ed9t s\u1ed1 \u0111\u1ec3 gi\u1ea3i b\u1ea5t ph\u01b0\u01a1ng tr\u00ecnh t\u1eeb \u0111\u00f3 t\u00ecm ra k\u1ebft qu\u1ea3 c\u1ea7n t\u00ecm.","explain":"<span class='basic_left'>Ta c\u00f3 $18 - 2x \\geq 0$<br\/>$\\Leftrightarrow 2x \\leq 18$<br\/>$\\Leftrightarrow x \\leq 18 : 2$<br\/>$\\Leftrightarrow x \\leq 9$<br\/>V\u1eady c\u00e1c nghi\u1ec7m nguy\u00ean d\u01b0\u01a1ng c\u1ee7a b\u1ea5t ph\u01b0\u01a1ng tr\u00ecnh l\u00e0 $x \\in \\left\\{1; 2; 3; 4; 5; 6; 7; 8; 9\\right\\}$ <br\/>\u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 <span class='basic_pink'>D. $x \\in \\left\\{1; 2; 3; 4; 5; 6; 7; 8; 9\\right\\}$<\/span><\/span>","column":2}],"id_ques":1255},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":10,"ques":"Gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh: $|4x - 1| = |5x + 2|$","select":[" A. $S = \\left\\{\\dfrac{-1}{9}; -3\\right\\}$"," B. $S = \\left\\{\\dfrac{1}{9}; 3\\right\\}$ ","C. $S = \\left\\{-3\\right\\}$","D. $S = \\left\\{-5 ; 3\\right\\}$"],"hint":"$|A(x)| = |B(x)| \\Leftrightarrow A(x) = \\pm B(x)$ ","explain":"<span class='basic_left'>Ta c\u00f3:<br\/>$|4x - 1| = |5x + 2|$ <br\/>$\\Leftrightarrow \\left[\\begin{array}{l} 4x - 1 = 5x + 2\\\\ 4x - 1 = -(5x + 2)\\end{array} \\right.$<br\/>$\\Leftrightarrow \\left[\\begin{array}{l} 5x - 4x = -1 - 2\\\\4x - 1 = -5x - 2\\end{array} \\right.$<br\/>$\\Leftrightarrow \\left[\\begin{array}{l} x = -3\\\\ 4x + 5x = -2 + 1\\end{array} \\right.$<br\/>$\\Leftrightarrow \\left[\\begin{array}{l} x = -3 \\\\ 9x = -1\\end{array} \\right.$<br\/>$\\Leftrightarrow \\left[\\begin{array}{l} x = -3 \\\\ x = \\dfrac{-1}{9}\\end{array} \\right.$<br\/>V\u1eady $S = \\left\\{\\dfrac{-1}{9}; -3\\right\\}$<br\/><span class='basic_pink'>\u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 A <\/span><br\/> ","column":2}],"id_ques":1256},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":10,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai29/lv3/img\/5.jpg' \/><\/center><br\/>Gi\u1ea3i b\u1ea5t ph\u01b0\u01a1ng tr\u00ecnh: $|5x - 1| < 2x + 5$","select":[" A. $\\dfrac{-4}{3} < x < 1$ "," B. $\\dfrac{-4}{3} < x < 2$","C. $\\dfrac{-4}{7} < x < 2$","D. $x > \\dfrac{-4}{7}$ "],"hint":"$|A| < |B| \\Leftrightarrow -B < A < B$.","explain":"<span class='basic_left'>Ta c\u00f3: <br\/>$|5x - 1| < 2x + 5 $<br\/>$\\Leftrightarrow -2x - 5 < 5x - 1 < 2x + 5$<br\/>$\\Leftrightarrow$ $\\left\\{\\begin{array}{l} -2x - 5 < 5x - 1\\\\5x - 1 < 2x + 5 \\end{array} \\right.$ <br\/>$\\Leftrightarrow$ $\\left\\{\\begin{array}{l} -5 + 1 < 5x + 2x\\\\5x - 2x < 5 + 1 \\end{array} \\right.$<br\/>$\\Leftrightarrow$ $\\left\\{\\begin{array}{l} 7x > -4\\\\3x < 6 \\end{array} \\right.$<br\/>$\\Leftrightarrow$ $\\left\\{\\begin{array}{l} x > \\dfrac{-4}{7} \\\\x < 2 \\end{array} \\right.$<br\/>$\\Leftrightarrow \\dfrac{-4}{7} < x < 2$<br\/>\u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 <span class='basic_pink'>C. $\\dfrac{-4}{7} < x < 2$<\/span><\/span>","column":2}],"id_ques":1257},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":10,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai29/lv3/img\/4.jpg' \/><\/center><br\/>Gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh: $\\left| x + \\dfrac{1}{1.2}\\right| + \\left| x + \\dfrac{1}{2.3}\\right| + ... + \\left| x + \\dfrac{1}{99.100}\\right| = 100x$ ","select":[" A. $x = \\dfrac{99}{100}$"," B. $x = \\dfrac{98}{100}$","C. $x = \\dfrac{98}{99}$","D. $x = \\dfrac{100}{99}$"],"hint":"","explain":"<span class='basic_left'>Nh\u1eadn th\u1ea5y v\u1ebf tr\u00e1i kh\u00f4ng \u00e2m v\u1edbi m\u1ecdi $x$ n\u00ean \u0111i\u1ec1u ki\u1ec7n c\u1ea7n \u0111\u1ec3 $x$ l\u00e0 nghi\u1ec7m c\u1ee7a ph\u01b0\u01a1ng tr\u00ecnh l\u00e0 v\u1ebf ph\u1ea3i kh\u00f4ng \u00e2m, t\u1ee9c l\u00e0: $100x \\geq 0 \\Leftrightarrow x \\geq 0$<br\/>Khi \u0111\u00f3 c\u00e1c bi\u1ec3u th\u1ee9c trong t\u1ea5t c\u1ea3 c\u00e1c d\u1ea5u gi\u00e1 tr\u1ecb tuy\u1ec7t \u0111\u1ed1i \u1edf v\u1ebf tr\u00e1i \u0111\u1ec1u d\u01b0\u01a1ng.<br\/>V\u00ec v\u1eady ph\u01b0\u01a1ng tr\u00ecnh tr\u1edf th\u00e0nh:<br\/>$\\left( x + \\dfrac{1}{1.2}\\right) + \\left( x + \\dfrac{1}{2.3}\\right) + ... + \\left( x + \\dfrac{1}{99.100}\\right) = 100x$<br\/> $\\Leftrightarrow \\left( \\dfrac{1}{1.2} + \\dfrac{1}{2.3} + ... + \\dfrac{1}{99.100}\\right) + 99x = 100x$<br\/>$\\Leftrightarrow x = \\dfrac{1}{1.2} + \\dfrac{1}{2.3} + ... + \\dfrac{1}{99.100}$<br\/>$\\Leftrightarrow x = 1- \\dfrac{1}{2} + \\dfrac{1}{2} - \\dfrac{1}{3} + \\dfrac{1}{3 } - ... + \\dfrac{1}{99} - \\dfrac{1}{100}$<br\/>$\\Leftrightarrow x = 1 - \\dfrac{1}{100}$<br\/>$\\Leftrightarrow x = \\dfrac{99}{100}$ (th\u1ecfa m\u00e3n \u0111i\u1ec1u ki\u1ec7n $x \\geq 0$)<br\/>V\u1eady ph\u01b0\u01a1ng tr\u00ecnh c\u00f3 nghi\u1ec7m duy nh\u1ea5t l\u00e0 $x = \\dfrac{99}{100}$<br\/><span class='basic_pink'>\u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 A<\/span><\/span> ","column":2}],"id_ques":1258},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":10,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai29/lv3/img\/3.jpg' \/><\/center><br\/>T\u00ecm $m$ \u0111\u1ec3 ph\u01b0\u01a1ng tr\u00ecnh $|6-7x| + 3 = 5m + 18$ v\u00f4 nghi\u1ec7m.","select":[" A. $m > 2$"," B. $m < -3$","C. $m > -3$","D. $m > -2$"],"hint":"","explain":"<span class='basic_left'><span class='basic_green'>Ph\u01b0\u01a1ng ph\u00e1p gi\u1ea3i:<\/span><br\/>Cho ph\u01b0\u01a1ng tr\u00ecnh c\u00f3 d\u1ea1ng $|P(x)| = k$ (trong \u0111\u00f3 $P(x)$ l\u00e0 bi\u1ec3u th\u1ee9c c\u1ee7a $x$, $k$ l\u00e0 m\u1ed9t s\u1ed1 cho tr\u01b0\u1edbc)<br\/>+ N\u1ebfu $k < 0$ th\u00ec ph\u01b0\u01a1ng tr\u00ecnh v\u00f4 nghi\u1ec7m<br\/>+ N\u1ebfu $k = 0$ th\u00ec ta c\u00f3 $|P(x)| = 0 \\Leftrightarrow P(x) = 0$ <br\/>+ N\u1ebfu $k > 0 $ th\u00ec ta c\u00f3 $|P(x)| = k \\Leftrightarrow \\left[\\begin{array}{l} P(x) = k \\\\ P(x) = -k\\end{array} \\right.$ <\/span> <br\/><span class='basic_left'><span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/>Ta c\u00f3: <br\/>$|6-7x| + 3 = 5m + 18 \\Leftrightarrow |6 - 7x| = 5m + 15$<br\/>Ph\u01b0\u01a1ng tr\u00ecnh v\u00f4 nghi\u1ec7m khi v\u00e0 ch\u1ec9 khi $5m + 15 < 0 \\Leftrightarrow 5m < -15 \\Leftrightarrow m < -3 $ <br\/>V\u1eady \u0111i\u1ec1u ki\u1ec7n c\u1ee7a $m$ l\u00e0 $m < -3$ <br\/><span class='basic_pink'>\u0110\u00e1p \u00e1n \u0111\u00fang l\u00e0 B<\/span><\/span> <br\/><\/span><br\/> ","column":2}],"id_ques":1259},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":10,"ques":"T\u00ecm $m$ \u0111\u1ec3 b\u1ea5t ph\u01b0\u01a1ng tr\u00ecnh sau nghi\u1ec7m \u0111\u00fang v\u1edbi m\u1ecdi $x \\in \\mathbb{R}$<br\/>$m^3(x - 2) \\leq m^2(x +1)$","select":[" A. $m = 0$"," B. $m = -1$ ","C. $m = -3$","D.$m = 3$"],"hint":"","explain":"<span class='basic_left'>Ta c\u00f3: $m^3(x - 2) \\leq m^2(x +1) \\Leftrightarrow m^3x - 2m^3 \\leq m^2x + m^2 \\Leftrightarrow m^3x - m^2x \\leq 2m^3 + m^2 \\Leftrightarrow (m^3 - m^2)x \\leq m^2(2m + 1)$<br\/>B\u1ea5t ph\u01b0\u01a1ng tr\u00ecnh nghi\u1ec7m \u0111\u00fang v\u1edbi m\u1ecdi $x \\in \\mathbb{R}$ khi v\u00e0 ch\u1ec9 khi:<br\/> $\\left\\{\\begin{array}{l} m^3 - m^2 = 0\\\\ m^2(2m + 1) \\geq 0 \\end{array} \\right.$<br\/>$\\Leftrightarrow$ $\\left\\{\\begin{array}{l} m^2(m - 1) = 0 \\\\ \\left\\{\\begin{array}{l}m^2 \\geq 0 \\hspace{0,2cm} \\forall x \\\\ 2m + 1 \\geq 0 \\end{array} \\right. \\end{array} \\right.$<br\/>$\\Leftrightarrow$ $\\left\\{\\begin{array}{l} \\left[\\begin{array}{l} m = 0\\\\ m = 1 \\end{array} \\right. \\\\ \\left\\{\\begin{array}{l}\\left[\\begin{array}{l} m \\geq 0 \\\\ m \\leq 0 \\end{array} \\right. \\\\ m \\leq \\dfrac{-1}{2} \\end{array} \\right. \\end{array} \\right.$<br\/> $\\Leftrightarrow$ $m = 0$<br\/>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 <span class='basic_pink'>A. $m = 0$<\/span><\/span><br\/><span class='basic_left'><span class='basic_green'>Nh\u1eadn x\u00e9t:<\/span><br\/> B\u1ea5t ph\u01b0\u01a1ng tr\u00ecnh d\u1ea1ng: $ax \\leq b$ v\u00f4 s\u1ed1 nghi\u1ec7m khi v\u00e0 ch\u1ec9 khi:<br\/> $\\left\\{\\begin{array}{l} a = 0 \\\\ b \\geq 0\\end{array} \\right.$<\/span> <br\/><br\/>","column":2}],"id_ques":1260}],"id_ques":0}],"lesson":{"save":1,"level":3,"time":44}}