{"common":{"save":0,"post_id":"1346","level":3,"total":10,"point":10,"point_extra":0},"segment":[{"id":"1881","post_id":"1346","mon_id":"0","chapter_id":"0","question":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","options":{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":10,"ques":"Cho \u0111\u01b0\u1eddng th\u1eb3ng $d$ v\u00e0 hai \u0111i\u1ec3m $A$, $B$ n\u1eb1m v\u1ec1 hai ph\u00eda c\u1ee7a \u0111\u01b0\u1eddng th\u1eb3ng $d$. V\u1ecb tr\u00ed \u0111i\u1ec3m $C$ tr\u00ean \u0111\u01b0\u1eddng th\u1eb3ng $d$ sao cho $CA + CB$ nh\u1ecf nh\u1ea5t l\u00e0: ","select":["A. $AC \\perp d$ ","B. $BC \\perp d$ ","C. $AB \\cap d = \\left\\{ C \\right\\}$ ","D. C\u1ea3 $3$ \u0111\u00e1p \u00e1n tr\u00ean \u0111\u1ec1u sai"],"hint":"","explain":" <span class='basic_left'><span class='basic_green'> B\u00e0i gi\u1ea3i:<\/span> <center><img src='img\/H7C3B19_K06.png' \/><\/center> <br\/> G\u1ecdi $C_{0}$ l\u00e0 giao \u0111i\u1ec3m c\u1ee7a $AB$ v\u00e0 \u0111\u01b0\u1eddng th\u1eb3ng $d$<br\/> $C$ l\u00e0 \u0111i\u1ec3m b\u1ea5t k\u00ec tr\u00ean \u0111\u01b0\u1eddng th\u1eb3ng $d$ <br\/> Trong $\\triangle{ABC}$, ta c\u00f3: <br\/> $AB < AC + BC$ (b\u1ea5t \u0111\u1eb3ng th\u1ee9c tam gi\u00e1c) <br\/> M\u1eb7t kh\u00e1c ta c\u00f3: $AC_{0} + C_{0}B = BC$ <br\/> $\\Leftrightarrow$ $AC_{0} + C_{0}B < AC + BC$ <br\/> V\u1eady \u0111\u1ec3 $CA + CB$ nh\u1ecf nh\u1ea5t th\u00ec $C \\equiv C_{0}$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: C <\/span> <br\/> <span class='basic_green'> <i> Nh\u1eadn x\u00e9t: B\u00e0i to\u00e1n tr\u00ean minh h\u1ecda ph\u01b0\u01a1ng ph\u00e1p t\u00ecm \u0111i\u1ec3m $C$ \u0111\u1ec3 $CA + CB$ nh\u1ecf nh\u1ea5t, trong tr\u01b0\u1eddng h\u1ee3p $A$, $B$ n\u1eb1m kh\u00e1c ph\u00eda \u0111\u1ed1i v\u1edbi \u0111\u01b0\u1eddng th\u1eb3ng $d$ <\/span> ","column":2}]}]},"correct":"","level":"3","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:23:05"},{"id":"1882","post_id":"1346","mon_id":"0","chapter_id":"0","question":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","options":{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":10,"ques":"Cho \u0111\u01b0\u1eddng th\u1eb3ng $d$ v\u00e0 hai \u0111i\u1ec3m $A$, $B$ n\u1eb1m v\u1ec1 m\u1ed9t ph\u00eda c\u1ee7a \u0111\u01b0\u1eddng th\u1eb3ng $d$ v\u00e0 $AB$ kh\u00f4ng song song v\u1edbi $d$. M\u1ed9t \u0111i\u1ec3m $M$ di \u0111\u1ed9ng tr\u00ean $d$. V\u1ecb tr\u00ed \u0111i\u1ec3m $M$ \u0111\u1ec3 $|MA - MB|$ l\u1edbn nh\u1ea5t l\u00e0: ","select":["A. $\\left\\{ M \\right\\} = AB \\cap d $ ","B. $BM \\perp d$ ","C. $AM \\perp d $ ","D. $IM \\perp d; IA = IB, I \\in AB$"],"hint":"","explain":" <span class='basic_left'><span class='basic_green'> B\u00e0i gi\u1ea3i:<\/span> <center><img src='img\/H7C3B19_K07.png' \/><\/center> <br\/> V\u00ec $AB$ kh\u00f4ng song song v\u1edbi $d$ n\u00ean g\u1ecdi $N$ l\u00e0 giao \u0111i\u1ec3m c\u1ee7a $AB$ v\u00e0 $d$, $M$ l\u00e0 \u0111i\u1ec3m b\u1ea5t k\u00ec tr\u00ean $d$ <br\/> V\u1edbi \u0111i\u1ec3m $M$ b\u1ea5t k\u00ec thu\u1ed9c \u0111\u01b0\u1eddng th\u1eb3ng $d$, $M$ kh\u00f4ng tr\u00f9ng v\u1edbi $N$ <br\/> \u00c1p d\u1ee5ng h\u1ec7 qu\u1ea3 c\u1ee7a b\u1ea5t \u0111\u1eb3ng th\u1ee9c tam gi\u00e1c cho $\\triangle{MAB}$, ta c\u00f3: <br\/> $|MA - MB| < AB$ (1) <br\/> Khi $M \\equiv N$ th\u00ec $|MA - MB| = AB$ (2) <br\/> T\u1eeb (1) v\u00e0 (2) $\\Rightarrow$ $|MA - MB|$ l\u1edbn nh\u1ea5t l\u00e0 b\u1eb1ng $AB$ khi $M \\equiv N$ l\u00e0 giao \u0111i\u1ec3m c\u1ee7a $AB$ v\u00e0 \u0111\u01b0\u1eddng th\u1eb3ng $d$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: A <\/span> <br\/> <span class='basic_green'> <i> Nh\u1eadn x\u00e9t: B\u00e0i to\u00e1n tr\u00ean minh h\u1ecda ph\u01b0\u01a1ng ph\u00e1p t\u00ecm \u0111i\u1ec3m $M$ \u0111\u1ec3 $MA - MB$ l\u1edbn nh\u1ea5t, trong tr\u01b0\u1eddng h\u1ee3p $A$, $B$ n\u1eb1m c\u00f9ng ph\u00eda \u0111\u1ed1i v\u1edbi \u0111\u01b0\u1eddng th\u1eb3ng $d$ <\/span> ","column":2}]}]},"correct":"","level":"3","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:23:05"},{"id":"1883","post_id":"1346","mon_id":"0","chapter_id":"0","question":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","options":{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":10,"ques":"Tam gi\u00e1c $ABC$ vu\u00f4ng t\u1ea1i $A$, tia ph\u00e2n gi\u00e1c g\u00f3c $B$ c\u1eaft $AC$ t\u1ea1i $D$. H\u00e3y so s\u00e1nh $BC - BA$ v\u1edbi $DC - DA$. ","select":["A. $BC - BA = DC - DA$ ","B. $BC - BA > DC - DA$ ","C. $BC - BA < DC - DA$ "],"hint":"\u0110\u1ec3 l\u00e0m xu\u1ea5t hi\u1ec7n hi\u1ec7u $BC - BA$, ta k\u1ebb $DH \\perp BC$ ","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/> <b> B\u01b0\u1edbc 1: <\/b> K\u1ebb $DH \\perp BC$ <br\/> Ch\u1ee9ng minh $BA = BH$; $DA = DH$ <br\/> <b> B\u01b0\u1edbc 2: <\/b> So s\u00e1nh $DC$ v\u00e0 $HC$ v\u00e0 $DC - DH$ v\u00e0 $HC$ <br\/> <b> B\u01b0\u1edbc 3: <\/b> T\u1eeb b\u01b0\u1edbc $1$ v\u00e0 b\u01b0\u1edbc $2$, bi\u1ebfn \u0111\u1ed5i v\u00e0 so s\u00e1nh $BC - BA$ v\u1edbi $DC - DA$ <br\/><br\/> <span class='basic_green'> B\u00e0i gi\u1ea3i:<\/span> <center><img src='img\/H7C3B19_K08.png' \/><\/center> <br\/> $\\blacktriangleright$ \u0110\u1ec3 l\u00e0m xu\u1ea5t hi\u1ec7n hi\u1ec7u $BC - BA$, ta k\u1ebb $DH \\perp BC$ <br\/> $\\blacktriangleright$ X\u00e9t hai tam gi\u00e1c vu\u00f4ng $BAD$ v\u00e0 $BHD$ c\u00f3: <br\/> $\\begin{cases} \\widehat{B_{1}} = \\widehat{B_{2}} (gt) \\\\ BD \\hspace{0,2cm} \\text{chung} \\end{cases}$ <br\/> $\\Rightarrow$ $\\triangle{BAD} = \\triangle{BHD}$ (c\u1ea1nh huy\u1ec1n - g\u00f3c nh\u1ecdn) <br\/> $\\Rightarrow$ $BA = BH$ v\u00e0 $DA = DH$ (hai c\u1ea1nh t\u01b0\u01a1ng \u1ee9ng) <br\/> $\\blacktriangleright$ $\\triangle{DHC}$ c\u00f3 $DC > DH$ (\u0111\u01b0\u1eddng xi\u00ean l\u1edbn h\u01a1n \u0111\u01b0\u1eddng vu\u00f4ng g\u00f3c) <br\/> $HC > DC - DH$ (h\u1ec7 qu\u1ea3 c\u1ee7a b\u1ea5t \u0111\u1eb3ng th\u1ee9c tam gi\u00e1c) (1) <br\/> M\u1eb7t kh\u00e1c ta c\u00f3: $HC = BC - BH = BC - BA$ (v\u00ec $BA = BH$) (2) <br\/> $DC - DH = DC - DA$ (v\u00ec $DH = DA$ (3) <br\/> $\\blacktriangleright$ T\u1eeb (1), (2), (3) $\\Rightarrow$ $BC - BA > DC - DA$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0: B <\/span> ","column":1}]}]},"correct":"","level":"3","hint":"","answer":"","type":"json","extra_type":"","time":"0","user_id":"0","test":"0","date":"2019-09-30 09:23:05"}]}