["C. x2 \uf02b y2 \uf02d 2x \uf02d y \uf02b1 \uf03d 0 . D. x2 \uf02b y2 \uf02b 6x \uf02b 5 y \uf02b1 \uf03d 0. Ch\u1ecdn A L\u1eddi gi\u1ea3i T\u00e2m I c\u1ee7a \u0111\u01b0\u1eddng tr\u00f2n l\u00e0 trung \u0111i\u1ec3m AB n\u00ean I \uf0281;3\uf029 . B\u00e1n k\u00ednh R \uf03d 1 AB \uf03d 1 \uf028\uf02d3 \uf02d 5\uf0292 \uf02b \uf0287 \uf02b1\uf0292 \uf03d 4 2. 2 2 V\u1eady ph\u01b0\u01a1ng tr\u00ecnh \u0111\u01b0\u1eddng tr\u00f2n l\u00e0: \uf028 x \uf02d1\uf0292 \uf02b \uf028 y \uf02d 3\uf0292 \uf03d 32 \uf0db x2 \uf02b y2 \uf02d 2x \uf02d 6 y \uf02d 22 \uf03d 0 . C\u00e2u 26: C\u00f3 bao nhi\u00eau s\u1ed1 t\u1ef1 nhi\u00ean c\u00f3 3 ch\u1eef s\u1ed1 \u0111\u00f4i m\u1ed9t kh\u00e1c nhau? A. 1000 . B. 720 . C. 729 . D. 648 . L\u1eddi gi\u1ea3i Ch\u1ecdn D G\u1ecdi s\u1ed1 c\u1ea7n l\u1eadp l\u00e0 abc c\u00f3 ba ch\u1eef s\u1ed1 \u0111\u00f4i m\u1ed9t kh\u00e1c nhau. Ch\u1eef s\u1ed1 a \uf0b9 0 : c\u00f3 9 c\u00e1ch ch\u1ecdn. Ch\u1eef s\u1ed1 b \uf0b9 a : c\u00f3 9 c\u00e1ch ch\u1ecdn. Ch\u1eef s\u1ed1 c \uf0b9 a,b : c\u00f3 8 c\u00e1ch ch\u1ecdn. \u00c1p d\u1ee5ng quy t\u1eafc nh\u00e2n ta c\u00f3 9.9.8 \uf03d 648 s\u1ed1. C\u00e2u 27: C\u00f3 10 qu\u1ea3 c\u1ea7u \u0111\u1ecf \u0111\u01b0\u1ee3c \u0111\u00e1nh s\u1ed1 t\u1eeb 1 \u0111\u1ebfn 10 , 7 qu\u1ea3 c\u1ea7u xanh \u0111\u01b0\u1ee3c \u0111\u00e1nh s\u1ed1 t\u1eeb 1 \u0111\u1ebfn 7 v\u00e0 8 qu\u1ea3 c\u1ea7u v\u00e0ng \u0111\u01b0\u1ee3c \u0111\u00e1nh s\u1ed1 t\u1eeb 1 \u0111\u1ebfn 8 . H\u1ecfi c\u00f3 bao nhi\u00eau c\u00e1ch l\u1ea5y ra 3 qu\u1ea3 c\u1ea7u kh\u00e1c m\u00e0u v\u00e0 kh\u00e1c s\u1ed1? A. 392 . B. 1023 . C. 3014 . D. 391. L\u1eddi gi\u1ea3i Ch\u1ecdn A Ta ch\u1ecdn c\u00e1c qu\u1ea3 c\u1ea7u theo tr\u00ecnh t\u1ef1 sau: Ch\u1ecdn qu\u1ea3 xanh: c\u00f3 7 c\u00e1ch ch\u1ecdn. Ch\u1ecdn qu\u1ea3 c\u1ea7u v\u00e0ng: c\u00f3 7 c\u00e1ch ch\u1ecdn (kh\u00e1c s\u1ed1 qu\u1ea3 c\u1ea7u xanh). Ch\u1ecdn qu\u1ea3 c\u1ea7u \u0111\u1ecf: c\u00f3 8 c\u00e1ch ch\u1ecdn (kh\u00e1c s\u1ed1 qu\u1ea3 c\u1ea7u xanh v\u00e0 v\u00e0ng). V\u1eady c\u00f3 t\u1ea5t c\u1ea3 7.7.8 \uf03d 392 c\u00e1ch ch\u1ecdn. C\u00e2u 28: M\u1ed9t l\u1edbp c\u00f3 15 h\u1ecdc sinh nam v\u00e0 20 h\u1ecdc sinh n\u1eef. C\u00f3 bao nhi\u00eau c\u00e1ch ch\u1ecdn 5 b\u1ea1n h\u1ecdc sinh sao cho trong \u0111\u00f3 c\u00f3 \u0111\u00fang 3 h\u1ecdc sinh n\u1eef? A. 110790. . B. 119700. . C. 117900. . D. 110970. L\u1eddi gi\u1ea3i. Ch\u1ecdn B S\u1ed1 c\u00e1ch ch\u1ecdn 3 h\u1ecdc sinh n\u1eef l\u00e0: C230 \uf03d 1140 c\u00e1ch. S\u1ed1 c\u00e1ch ch\u1ecdn 2 b\u1ea1n h\u1ecdc sinh nam l\u00e0: C125 \uf03d 105 c\u00e1ch. S\u1ed1 c\u00e1ch ch\u1ecdn 5 b\u1ea1n th\u1ecfa m\u00e3n y\u00eau c\u1ea7u b\u00e0i to\u00e1n l\u00e0: 1140.105 \uf03d 119700 c\u00e1ch. C\u00e2u 29: Trong m\u1ed9t bu\u1ed5i khi\u00eau v\u0169 c\u00f3 20 nam v\u00e0 18 n\u1eef. H\u1ecfi c\u00f3 bao nhi\u00eau c\u00e1ch ch\u1ecdn ra m\u1ed9t \u0111\u00f4i nam n\u1eef \u0111\u1ec3 khi\u00eau v\u0169?","A. C328 . B. A328 . C. C220C118 . D. C210C118 . Ch\u1ecdn D L\u1eddi gi\u1ea3i Ch\u1ecdn m\u1ed9t nam trong 20 nam c\u00f3 C210 c\u00e1ch. Ch\u1ecdn m\u1ed9t n\u1eef trong 18 n\u1eef c\u00f3 C118 c\u00e1ch. Theo quy t\u1eafc nh\u00e2n, s\u1ed1 c\u00e1ch ch\u1ecdn m\u1ed9t \u0111\u00f4i nam n\u1eef l\u00e0 C210C118 . C\u00e2u 30: T\u00ecm h\u1ec7 s\u1ed1 c\u1ee7a x2 y2 trong khai tri\u1ec3n nh\u1ecb th\u1ee9c Newton c\u1ee7a \uf028 x \uf02b 2 y\uf0294 . A. 32 . B. 8 . C. 24 . D. 16 . Ch\u1ecdn C L\u1eddi gi\u1ea3i \uf0e5 \uf0e5Ta c\u00f3 \uf028 x \uf02b 2 y \uf0294 \uf03d 4 \uf028 \uf029C4k x4\uf02dk 2 y k \uf03d 4 C4k .2k.x4\uf02dk yk . k \uf03d0 k\uf03d0 S\u1ed1 h\u1ea1ng ch\u1ee9a x2 y2 trong khai tri\u1ec3n tr\u00ean \u1ee9ng v\u1edbi \uf0ec4 \uf02dk \uf03d 2 \uf0db k \uf03d 2. \uf0ed\uf0eek \uf03d2 V\u1eady h\u1ec7 s\u1ed1 c\u1ee7a x2 y2 trong khai tri\u1ec3n c\u1ee7a \uf028 x \uf02b 2 y\uf0294 l\u00e0 C42.22 \uf03d 24 . C\u00e2u 31: T\u00ecm s\u1ed1 h\u1ea1ng ch\u1ee9a x2 trong khai tri\u1ec3n nh\u1ecb th\u1ee9c Newton c\u1ee7a P \uf028 x\uf029 \uf03d 4x2 \uf02b x \uf028 x \uf02d 2\uf0294 . A. 28x2 . B. \uf02d28x2 . C. \uf02d24x2 . D. 24x2 . Ch\u1ecdn B L\u1eddi gi\u1ea3i \uf0e5 \uf0e5Ta c\u00f3 P \uf028 x\uf029 \uf03d 4x2 \uf02b x \uf028 x \uf02d 2\uf0294 \uf03d 4x2 \uf02b x 4 \uf028 \uf029C4k x4\uf02dk \uf02d2 k \uf03d 4x2 \uf02b 4 \uf028 \uf029C4k \uf02d2 k x5\uf02dk . k \uf03d0 k \uf03d0 S\u1ed1 h\u1ea1ng ch\u1ee9a x2 (\u1ee9ng v\u1edbi k \uf03d 3) trong khai tri\u1ec3n P\uf028x\uf029 l\u00e0 \uf0e9\uf0eb4 \uf02b C43 \uf028 \uf02d2 \uf0293 \uf0f9 x 2 \uf03d \uf02d28x2 . \uf0fb C\u00e2u 32: M\u1ed9t \u0111\u1ed9i thanh ni\u00ean t\u00ecnh nguy\u1ec7n g\u1ed3m 12 nam v\u00e0 3 n\u1eef \u0111\u01b0\u1ee3c ph\u00e2n c\u00f4ng ng\u1eabu nhi\u00ean v\u1ec1 3 t\u1ec9nh, m\u1ed7i t\u1ec9nh 5 ng\u01b0\u1eddi. T\u00ednh s\u1ed1 ph\u1ea7n t\u1eed c\u1ee7a kh\u00f4ng gian m\u1eabu A. C155.C154.C153 . B. C155.C150.C55 . C. C155 . D. C142.C31 . L\u1eddi gi\u1ea3i Ch\u1ecdn C Ch\u1ecdn 5 ng\u01b0\u1eddi t\u1eeb 15 ng\u01b0\u1eddi v\u1ec1 t\u1ec9nh th\u1ee9 nh\u1ea5t c\u00f3 C155 c\u00e1ch. Ch\u1ecdn 5 ng\u01b0\u1eddi t\u1eeb 10 ng\u01b0\u1eddi c\u00f2n l\u1ea1i v\u1ec1 t\u1ec9nh th\u1ee9 hai c\u00f3 C150 c\u00e1ch. Ch\u1ecdn 5 ng\u01b0\u1eddi t\u1eeb 5 ng\u01b0\u1eddi v\u1ec1 t\u1ec9nh th\u1ee9 ba c\u00f3 C55 c\u00e1ch ch\u1ecdn. Suy ra c\u00f3 C155.C150.C55 c\u00e1ch ph\u00e2n c\u00f4ng 15 ng\u01b0\u1eddi v\u1ec3 3 t\u1ec9nh, m\u1ed7i t\u1ec9nh 5 ng\u01b0\u1eddi. V\u1eady s\u1ed1 ph\u1ea7n t\u1eed c\u1ee7a kh\u00f4ng gian m\u1eabu l\u00e0 C155.C150.C55 .","C\u00e2u 33: Gieo m\u1ed9t con s\u00fac s\u1ed9c c\u00e2n \u0111\u1ed9i, \u0111\u1ed9ng ch\u1ed9t v\u00e0 quan s\u00e1t s\u1ed9 ch\u1ed9m xu\u1ed9t hi\u1ed9n. S\u1ed9 ph\u1ed9n t\u1ed9 c\u1ed9a bi\u1ed9n c\u1ed9 A: \u201dXu\u1ed9t hi\u1ed9n m\u1ed9t c\u00f3 s\u1ed9 ch\u1ed9m kh\u00f4ng nh\u1ed9 h\u1ed9n 2\u201d l\u00e0 A. 3. B. 4. C. 5. D. 6 Ch\u1ecdn C L\u1eddi gi\u1ea3i Bi\u1ed9n c\u1ed9 A x\u1ed9y ra khi m\u1ed9t c\u00f3 s\u1ed9 ch\u1ed9m kh\u00f4ng nh\u1ed9 h\u1ed9n 2 xu\u1ed9t hi\u1ed9n V\u1ed9y A={2, 3, 4, 5, 6}. C\u00e2u 34: M\u1ed9t l\u1ed9p c\u00f3 20 h\u1ed9c sinh nam v\u00e0 18 h\u1ed9c sinh n\u1ed9. Ch\u1ed9n ng\u1ed9u nhi\u00ean m\u1ed9t h\u1ed9c sinh.X\u00e1c su\u1ed9t ch\u1ed9n \u0111\u1ed9\u1ed9c 1 h\u1ed9c sinh n\u1ed9 l\u00e0 A. 1 . B. 10 . C. 9 . D. 7 . 38 19 19 19 L\u1eddi gi\u1ea3i Ch\u1ecdn C S\u1ed9 ph\u1ed9n t\u1ed9 c\u1ed9a kh\u00f4ng gian m\u1ed9u n\uf028\uf057\uf029 \uf03d 38 . S\u1ed9 ph\u1ed9n t\u1ed9 c\u1ed9a bi\u1ed9n c\u1ed9 A : \u201cCh\u1ed9n \u0111\u1ed9\u1ed9c m\u1ed9t h\u1ed9c sinh n\u1ed9\u201d l\u00e0 n\uf028 A\uf029 \uf03d 18 . \uf0de P \uf028 A\uf029 \uf03d 18 \uf03d 9 . 38 19 C\u00e2u 35: M\u1ed9t b\u00ecnh \u0111\u1ed9ng 4 qu\u1ed9 c\u1ed9u xanh v\u00e0 6 qu\u1ed9 c\u1ed9u tr\u1ed9ng. Ch\u1ed9n ng\u1ed9u nhi\u00ean 2 qu\u1ed9 c\u1ed9u. X\u00e1c su\u1ed9t \u0111\u1ed9 ch\u1ed9n \u0111\u1ed9\u1ed9c 2 qu\u1ed9 c\u1ed9u c\u00f3 \u0111\u1ed9 hai m\u00e0u l\u00e0 A. 5 . B. 7 . C. 2 . D. 8 . 9 15 9 15 L\u1eddi gi\u1ea3i Ch\u1ecdn D S\u1ed9 ph\u1ed9n t\u1ed9 c\u1ed9a kh\u00f4ng gian m\u1ed9u n \uf028\uf057\uf029 \uf03d C120 \uf03d 45 . S\u1ed9 ph\u1ed9n t\u1ed9 c\u1ed9a bi\u1ed9n c\u1ed9 A : \u201cCh\u1ed9n \u0111\u1ed9\u1ed9c 2 qu\u1ed9 c\u1ed9u c\u00f3 \u0111\u1ed9 hai m\u00e0u\u201d l\u00e0 4.6 \uf03d 24 . \uf0de P \uf028 A\uf029 \uf03d 24 \uf03d 8 . 45 15 II. PH\u1ea6N T\u1ea6 LU\u1ea6N C\u00e2u 36: T\u1eeb c\u00e1c ch\u1eef s\u1ed1 1, 2,3, 4,5, 6 c\u00f3 th\u1ec3 l\u1eadp \u0111\u01b0\u1ee3c bao nhi\u00eau s\u1ed1 t\u1ef1 nhi\u00ean l\u1ebb c\u00f3 6 ch\u1eef s\u1ed1 kh\u00e1c nhau v\u00e0 trong m\u1ed7i s\u1ed1 \u0111\u00f3 t\u1ed5ng c\u1ee7a ba ch\u1eef s\u1ed1 \u0111\u1ea7u l\u1edbn h\u01a1n t\u1ed5ng c\u1ee7a ba ch\u1eef s\u1ed1 cu\u1ed1i m\u1ed9t \u0111\u01a1n v\u1ecb. L\u1eddi gi\u1ea3i G\u1ecdi a1a2a3a4a5a6 l\u00e0 s\u1ed1 c\u1ea7n t\u00ecm. Ta c\u00f3 a6 \uf0ce\uf07b1;3;5\uf07d v\u00e0 \uf028a1 \uf02b a2 \uf02b a3 \uf029 \uf02d \uf028a4 \uf02b a5 \uf02b a6 \uf029 \uf03d 1","- V\u1edbi a6 \uf03d 1 th\u00ec \uf028a1 \uf02b a2 \uf02b a3 \uf029 \uf02d \uf028a4 \uf02b a5 \uf029 \uf03d 2 \uf0de \uf0ef\uf0ec\uf0ed\uf0ef\uf0eeaa14,,aa25,\uf0cea3\uf07b\uf0ce4,\uf07b52\uf07d,3, 6\uf07d ho\u1eb7c - V\u1edbi a6 \uf03d3 th\u00ec \uf0ec\uf0ee\uf0ef\uf0ed\uf0efaa14,,aa25,\uf0cea3\uf07b\uf0ce3,\uf07b62\uf07d, 4,5\uf07d\uf028a1 \uf02b a2 \uf02b a3 \uf029 \uf02d \uf028a4 \uf02b a5 \uf029 \uf03d 4 \uf0de \uf0ed\uf0ef\uf0ec\uf0ef\uf0eeaa14,,aa25,\uf0cea3\uf07b1\uf0ce, \uf07b2; 4; 5\uf07d 6\uf07d ho\u1eb7c \uf0ec\uf0ed\uf0ef\uf0ee\uf0efaa14,,aa25,\uf0cea3\uf07b\uf0ce2,\uf07b51\uf07d, 4, 6\uf07d - V\u1edbi a6 \uf03d5 th\u00ec \uf028a1 \uf02b a2 \uf02b a3 \uf029 \uf02d \uf028a4 \uf02b a5 \uf029 \uf03d 6 \uf0de \uf0ef\uf0ef\uf0ed\uf0ec\uf0eeaa14,,aa25,\uf0cea3\uf07b\uf0ce1, \uf07b2, 3, 6\uf07d ho\u1eb7c \uf0ef\uf0ed\uf0ef\uf0ee\uf0ecaa14,,aa25,\uf0cea3\uf07b\uf0ce2,\uf07b31\uf07d, 4, 6\uf07d 4\uf07d M\u1ed7i tr\u01b0\u1eddng h\u1ee3p c\u00f3 3!\uf0d7 2! \uf03d 12 s\u1ed1 th\u1ecfa m\u00e3n y\u00eau c\u1ea7u V\u1eady c\u00f3 t\u1ea5t c\u1ea3 6.12 \uf03d 72 s\u1ed1 c\u1ea7n t\u00ecm. C\u00e2u 37: \u0110\u1ec3 chu\u1ea9n b\u1ecb k\u1ef7 ni\u1ec7m 50 n\u0103m th\u00e0nh l\u1eadp tr\u01b0\u1eddng THPT, nh\u00e0 tr\u01b0\u1eddng th\u00e0nh l\u1eadp hai t\u1ed5 h\u1ecdc sinh \u0111\u1ec3 \u0111\u00f3n ti\u1ebfp c\u00e1c v\u1ecb \u0111\u1ea1i bi\u1ec3u. T\u1ed5 m\u1ed9t g\u1ed3m 3 h\u1ecdc sinh l\u1edbp 12A1 v\u00e0 2 h\u1ecdc sinh l\u1edbp 12A2 ; t\u1ed5 hai g\u1ed3m 3 h\u1ecdc sinh l\u1edbp 12A1 v\u00e0 4 h\u1ecdc sinh l\u1edbp 12A3 . Ch\u1ecdn ng\u1eabu nhi\u00ean t\u1eeb m\u1ed7i t\u1ed5 ra 2 h\u1ecdc sinh, t\u00ednh x\u00e1c su\u1ea5t \u0111\u1ec3 trong 4 h\u1ecdc sinh \u0111\u01b0\u1ee3c ch\u1ecdn c\u00f3 \u0111\u1ee7 h\u1ecdc sinh c\u1ee7a ba l\u1edbp. L\u1eddi gi\u1ea3i Kh\u00f4ng gian m\u1eabu l\u00e0 s\u1ed1 c\u00e1ch ch\u1ecdn ng\u1eabu nhi\u00ean m\u1ed7i t\u1ed5 ra 2 h\u1ecdc sinh. Suy ra s\u1ed1 ph\u1ea7n t\u1eed c\u1ee7a kh\u00f4ng gian m\u1eabu l\u00e0 n \uf028\uf057\uf029 \uf03d C52.C72 \uf03d 210 . G\u1ecdi A l\u00e0 bi\u1ebfn c\u1ed1 '' 4 h\u1ecdc sinh \u0111\u01b0\u1ee3c ch\u1ecdn c\u00f3 \u0111\u1ee7 ba l\u1edbp '' . Ta m\u00f4 t\u1ea3 c\u00e1c tr\u01b0\u1eddng h\u1ee3p thu\u1eadn l\u1ee3i cho bi\u1ebfn c\u1ed1 A nh\u01b0 sau: \u25cf Tr\u01b0\u1eddng h\u1ee3p 1. T\u1ed5 m\u1ed9t ch\u1ecdn 1 h\u1ecdc sinh l\u1edbp 12A1 , 1 h\u1ecdc sinh l\u1edbp 12A2 . T\u1ed5 hai ch\u1ecdn 1 h\u1ecdc sinh l\u1edbp 12A1 , 1 h\u1ecdc sinh l\u1edbp 12A3 . Do \u0111\u00f3 tr\u01b0\u1eddng h\u1ee3p n\u00e0y c\u00f3 C31.C21.C31.C41 \uf03d 72 c\u00e1ch. \u25cf Tr\u01b0\u1eddng h\u1ee3p 2. T\u1ed5 m\u1ed9t ch\u1ecdn 1 h\u1ecdc sinh l\u1edbp 12A1 , 1 h\u1ecdc sinh l\u1edbp 12A2 . T\u1ed5 hai ch\u1ecdn 2 h\u1ecdc sinh l\u1edbp 12A3 . Do \u0111\u00f3 tr\u01b0\u1eddng h\u1ee3p n\u00e0y c\u00f3 C31.C21.C42 \uf03d 36 c\u00e1ch. \u25cf Tr\u01b0\u1eddng h\u1ee3p 3. T\u1ed5 m\u1ed9t ch\u1ecdn 2 h\u1ecdc sinh l\u1edbp 12A2 . T\u1ed5 hai ch\u1ecdn 1 h\u1ecdc sinh l\u1edbp 12A1 , 1 h\u1ecdc sinh l\u1edbp 12A3 . Do \u0111\u00f3 tr\u01b0\u1eddng h\u1ee3p n\u00e0y c\u00f3 C22.C31.C41 \uf03d 12 c\u00e1ch. Suy ra s\u1ed1 ph\u1ea7n t\u1eed c\u1ee7a bi\u1ebfn c\u1ed1 A l\u00e0 n \uf028 A\uf029 \uf03d 72 \uf02b 36 \uf02b12 \uf03d 120. V\u1eady x\u00e1c su\u1ea5t c\u1ea7n t\u00ednh P\uf028 A\uf029 \uf03d n \uf028 A\uf029 \uf03d 120 \uf03d 4 . . n\uf028\uf057\uf029 210 7 C\u00e2u 38: C\u00f3 bao nhi\u00eau s\u1ed1 t\u1ef1 nhi\u00ean g\u1ed3m 7 ch\u1eef s\u1ed1 trong \u0111\u00f3 ch\u1eef s\u1ed1 2 c\u00f3 m\u1eb7t \u0111\u00fang hai l\u1ea7n, ch\u1eef s\u1ed1 3 c\u00f3 m\u1eb7t \u0111\u00fang ba l\u1ea7n v\u00e0 c\u00e1c ch\u1eef s\u1ed1 c\u00f2n l\u1ea1i c\u00f3 m\u1eb7t kh\u00f4ng qu\u00e1 m\u1ed9t l\u1ea7n? L\u1eddi gi\u1ea3i D\u00f9ng 7 \u00f4 sau \u0111\u1ec3 thi\u1ebft l\u1eadp s\u1ed1 c\u00f3 7 ch\u1eef s\u1ed1: \uf02a Ch\u1ecdn 2 \u00f4 \u0111\u1ec3 x\u1ebfp 2 s\u1ed1 2: c\u00f3 C72 c\u00e1ch; Ch\u1ecdn 3 \u00f4 \u0111\u1ec3 x\u1ebfp 3 s\u1ed1 3: c\u00f3 C53 c\u00e1ch;","Ch\u1ecdn 2 s\u1ed1 ( kh\u00e1c 2 v\u00e0 3 ) x\u1ebfp v\u00e0o 2 \u00f4 c\u00f2n l\u1ea1i: c\u00f3 A82 c\u00e1ch; \uf0de C\u00f3 C72.C53.A82 \uf03d 11760 s\u1ed1 ( c\u00f3 k\u1ec3 s\u1ed1 c\u00f3 s\u1ed1 0 \u0111\u1ee9ng \u0111\u1ea7u ). \uf02a Khi s\u1ed1 0 \u0111\u1ee9ng \u00f4 th\u1ee9 nh\u1ea5t, ta c\u00f3: \uf02b C\u00f3 C62 c\u00e1ch x\u1ebfp 2 s\u1ed1 2; \uf02b C\u00f3 C43 c\u00e1ch x\u1ebfp 3 s\u1ed1 3; \uf02b C\u00f3 8 c\u00e1ch x\u1ebfp s\u1ed1 v\u00e0o \u00f4 c\u00f2n l\u1ea1i; \uf0de C\u00f3 C62.C43.8 \uf03d 480 s\u1ed1 m\u00e0 ch\u1eef s\u1ed1 0 \u0111\u1ee9ng \u0111\u1ea7u. V\u1eady s\u1ed1 c\u00e1c s\u1ed1 l\u1eadp \u0111\u01b0\u1ee3c l\u00e0 13440 \uf02d 480 \uf03d 11280 . C\u00e2u 39: G\u1ecdi S l\u00e0 t\u1eadp h\u1ee3p c\u00e1c s\u1ed1 t\u1ef1 nhi\u00ean c\u00f3 6 ch\u1eef s\u1ed1. Ch\u1ecdn ng\u1eabu nhi\u00ean m\u1ed9t s\u1ed1 t\u1eeb S , t\u00ednh x\u00e1c su\u1ea5t \u0111\u1ec3 c\u00e1c ch\u1eef s\u1ed1 c\u1ee7a s\u1ed1 \u0111\u00f3 \u0111\u00f4i m\u1ed9t kh\u00e1c nhau v\u00e0 ph\u1ea3i c\u00f3 m\u1eb7t ch\u1eef s\u1ed1 0 v\u00e0 1. L\u1eddi gi\u1ea3i S\u1ed1 ph\u1ea7n t\u1eed c\u1ee7a S b\u1eb1ng 9.105 . X\u00e9t ph\u00e9p th\u1eed ch\u1ecdn ng\u1eabu nhi\u00ean m\u1ed9t s\u1ed1 t\u1eeb S , ta \u0111\u01b0\u1ee3c n\uf028\uf057\uf029 \uf03d 9.105 . G\u1ecdi A l\u00e0 bi\u1ebfn c\u1ed1 \u201c Ch\u1ecdn \u0111\u01b0\u1ee3c s\u1ed1 c\u00f3 c\u00e1c ch\u1eef s\u1ed1 \u0111\u00f4i m\u1ed9t kh\u00e1c nhau v\u00e0 ph\u1ea3i c\u00f3 m\u1eb7t ch\u1eef s\u1ed1 0 v\u00e0 1\u201d. Ta c\u00f3 c\u00e1c tr\u01b0\u1eddng h\u1ee3p sau. Gi\u1ea3 s\u1eed s\u1ed1 ch\u1ecdn \u0111\u01b0\u1ee3c c\u00f3 d\u1ea1ng: a1a2...a6 Tr\u01b0\u1eddng h\u1ee3p 1: a1 \uf03d 1. S\u1ed1 c\u00e1ch ch\u1ecdn v\u1ecb tr\u00ed cho s\u1ed1 0 l\u00e0 5 c\u00e1ch. S\u1ed1 c\u00e1ch ch\u1ecdn 4 ch\u1eef s\u1ed1 c\u00f2n l\u1ea1i l\u00e0 A84 c\u00e1ch. V\u1eady tr\u01b0\u1eddng h\u1ee3p n\u00e0y c\u00f3 1.5.A84 s\u1ed1. Tr\u01b0\u1eddng h\u1ee3p 2: a1 \uf0b9 1 \uf0de a1 c\u00f3 8 c\u00e1ch ch\u1ecdn. S\u1ed1 c\u00e1ch ch\u1ecdn v\u1ecb tr\u00ed cho hai ch\u1eef s\u1ed1 0;1 l\u00e0 A52 . S\u1ed1 c\u00e1ch ch\u1ecdn ba s\u1ed1 c\u00f2n l\u1ea1i l\u00e0 A73 . V\u1eady tr\u01b0\u1eddng h\u1ee3p n\u00e0y c\u00f3 8.A52.A73 s\u1ed1. Suy ra PA \uf03d 5.A84 \uf02b 8.A52.A73 \uf03d 7 . 9.105 150"]
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