Th\u1ea1c s\u0129 Nguy\u1ec5n V\u0169 Minh (Bi\u00ean H\u00f2a, \u0110\u1ed3ng Nai) ch\u1ec9 ra m\u1ed9t s\u1ed1 l\u1ed7i c\u01a1 b\u1ea3n th\u00ed sinh c\u1ea7n bi\u1ebft \u0111\u1ec3 tr\u00e1nh m\u1ea5t \u0111i\u1ec3m khi l\u00e0m \u0111\u1ec1 th\u00ec m\u00f4n To\u00e1n THPT qu\u1ed1c gia.<\/strong><\/em><\/p>\n

<\/p>\n

Trong \u0111\u1ec1 thi THPT qu\u1ed1c gia m\u00f4n To\u00e1n, c\u00f3 r\u1ea5t nhi\u1ec1u nh\u1eefng l\u1ed7i c\u00e1c b\u1ea1n th\u00ed sinh th\u01b0\u1eddng g\u1eb7p ph\u1ea3i d\u1eabn t\u1edbi m\u1ea5t \u0111i\u1ec3m trong \u0111\u1ec1 thi. Trao \u0111\u1ed5i v\u1edbi ch\u00fang t\u00f4i, gi\u00e1o vi\u00ean V\u0169 Minh chia s\u1ebb: \u201c\u0110\u00e2y \u0111\u1ec1u l\u00e0 nh\u1eefng l\u1ed7i c\u01a1 b\u1ea3n v\u00e0 nh\u1ecf nh\u1eb7t nh\u01b0ng c\u00e1c b\u1ea1n h\u1ecdc sinh l\u1ea1i th\u01b0\u1eddng m\u1ea5t \u0111i\u1ec3m u\u1ed5ng ph\u00ed v\u00ec n\u00f3\u201d.<\/p>\n

Ph\u1ea7n kh\u1ea3o s\u00e1t h\u00e0m s\u1ed1<\/strong><\/p>\n

\u0110\u1ed1i v\u1edbi ph\u1ea7n n\u00e0y, th\u00ed sinh c\u1ea7n \u00f4n t\u1eadp c\u00e1c d\u1ea1ng \u0111\u1ed3 th\u1ecb, c\u1ef1c tr\u1ecb, ti\u1ebfp tuy\u1ebfn, t\u00ednh \u0111\u01a1n \u0111i\u1ec7u, s\u1ef1 t\u01b0\u01a1ng giao (b\u1eb1ng \u0111\u1ed3 th\u1ecb ho\u1eb7c ph\u00e9p to\u00e1n)… \u1edf m\u1ee9c c\u01a1 b\u1ea3n \u0111\u1ec3 gi\u1ea3i quy\u1ebft nh\u1eefng c\u00e2u \u0111\u01a1n gi\u1ea3n tr\u00e1nh m\u1ea5t \u0111i\u1ec3m oan v\u00ec n\u00f3.<\/p>\n

V\u00ed d\u1ee5: Cho h\u00e0m s\u1ed1 y = (x+2)(x^{2<\/sup>\u00a0+1) c\u00f3 \u0111\u1ed3 th\u1ecb (C). M\u1ec7nh \u0111\u1ec1 n\u00e0o d\u01b0\u1edbi \u0111\u00e2y \u0111\u00fang?<\/p>\n}

A. (C) C\u1eaft tr\u1ee5c ho\u00e0nh t\u1ea1i hai \u0111i\u1ec3m.<\/p>\n

B. (C) C\u1eaft tr\u1ee5c ho\u00e0nh t\u1ea1i m\u1ed9t \u0111i\u1ec3m.<\/p>\n

C. (C) Kh\u00f4ng c\u1eaft tr\u1ee5c ho\u00e0nh.<\/p>\n

D. (C) C\u1eaft tr\u1ee5c ho\u00e0nh t\u1ea1i ba \u0111i\u1ec3m.<\/p>\n

\u0110\u00e2y l\u00e0 d\u1ea1ng t\u01b0\u01a1ng giao \u0111\u1ed3 th\u1ecb d\u1ea1ng c\u01a1 b\u1ea3n, ta ch\u1ec9 c\u1ea7n d\u00f9ng ph\u01b0\u01a1ng tr\u00ecnh ho\u00e0nh \u0111\u1ed9 \u0111i\u1ec3m chung (cho y = 0) s\u1ebd ra nghi\u1ec7m x = \u2013 2 v\u00e0 ch\u1ecdn B ( \u1edf \u0111\u00e2y ch\u00fa \u00fd x^{2<\/sup>\u00a0+ 1 >0 ).<\/p>\n}

\u1ede \u0111\u00e2y, ch\u1ec9 c\u1ea7n \u0111\u1ec3 \u00fd s\u1ebd th\u1ea5y ch\u1ec9 c\u00f3 m\u1ed9t nghi\u1ec7m duy nh\u1ea5t m\u00e0 kh\u00f4ng c\u1ea7n b\u1ea5m m\u00e1y c\u0169ng s\u1ebd nh\u1eadn \u0111\u01b0\u1ee3c \u0111\u00e1p \u00e1n.<\/p>\n

Ph\u1ea7n s\u1ed1 ph\u1ee9c<\/strong><\/p>\n

Ri\u00eang ph\u1ea7n s\u1ed1 ph\u1ee9c, h\u1ecdc sinh c\u1ea7n \u0111\u1ecdc k\u0129 \u0111\u1ec1 \u0111\u1ec3 tr\u00e1nh nh\u1ea7m l\u1eabn ph\u1ea7n th\u1ef1c v\u00e0 \u1ea3o d\u1eabn t\u1edbi m\u1ea5t \u0111i\u1ec3m trong \u0111\u1ec1 thi.<\/p>\n

V\u00ed d\u1ee5 1: Cho s\u1ed1 ph\u1ee9c z = 6 + 7i. S\u1ed1 ph\u1ee9c li\u00ean h\u1ee3p c\u1ee7a z c\u00f3 \u0111i\u1ec3m bi\u1ec3u di\u1ec5n l\u00e0<\/p>\n

A. (6; \u20137). B. (6; 7). C(\u20136;7). D. (\u20136; \u20137).<\/p>\n

\u1ede \u0111\u00e2y h\u1ecdc sinh c\u00f3 m\u1ed9t s\u1ed1 th\u00f3i quen nh\u00ecn v\u00e0o bi\u1ec3u th\u1ee9c s\u1ed1 ph\u1ee9c n\u00e0y kh\u00f4ng \u0111\u1ecdc k\u0129 d\u1eabn \u0111\u1ebfn nh\u1ea7m l\u1eabn t\u00ecm bi\u1ec3u di\u1ec5n s\u1ed1 ph\u1ee9c z s\u1ebd ch\u1ecdn B. Nh\u01b0ng \u1edf \u0111\u00e2y \u0111\u1ec1 cho l\u00e0 t\u00ecm bi\u1ec3u di\u1ec5n s\u1ed1 ph\u1ee9c li\u00ean h\u1ee3p n\u00ean ph\u1ea3i l\u1ea5y li\u00ean h\u1ee3p ph\u1ee9c l\u00e0 6 \u2013 7i. \u0110\u00e1p \u00e1n \u1edf \u0111\u00e2y l\u00e0 A.<\/p>\n

V\u00ed d\u1ee5 2: Cho s\u1ed1 ph\u1ee9c z = \u20132i \u2013 1. \u0110i\u1ec3m bi\u1ec3u di\u1ec5n s\u1ed1 ph\u1ee9c li\u00ean h\u1ee3p c\u1ee7a z l\u00e0:<\/p>\n

A. M(\u20132;1) B. M(\u20131; \u20132) C. M(\u20132;1) D. M(2; \u20131)<\/p>\n

\u1ede ph\u1ea7n n\u00e0y, n\u1ebfu kh\u00f4ng nh\u00ecn k\u0129 h\u1ecdc sinh d\u1ec5 nh\u1ea7m th\u00e0nh \u0111\u00e1p \u00e1n D thay v\u00ec \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A. V\u00ec \u0111\u1ec1 \u0111\u00e3 \u0111\u1ed5i v\u1ecb tr\u00ed thay v\u00ec ghi z = \u20131\u20132i l\u1ea1i ghi z = \u20132i \u2013 1 .<\/p>\n

Ph\u1ea7n h\u00ecnh gi\u1ea3i t\u00edch kh\u00f4ng gian<\/strong><\/p>\n

H\u1ecdc sinh s\u1ebd r\u1ea5t d\u1ec5 b\u1ecb nh\u1ea7m l\u1eabn n\u1ebfu kh\u00f4ng \u0111\u1ecdc k\u0129 ph\u01b0\u01a1ng tr\u00ecnh \u1edf ph\u1ea7n n\u00e0y.<\/p>\n

V\u00ed d\u1ee5: N\u1ebfu \u0111\u1ec1 b\u00e0i cho ph\u01b0\u01a1ng tr\u00ecnh \u0111\u01b0\u1eddng th\u1eb3ng d d\u1ea1ng ch\u00ednh t\u1eafc l\u00e0<\/p>\n

(x \u2013 1)\/1 = (y \u2013 2)\/2 = (2 \u2013 z)\/3<\/p>\n

s\u1ebd d\u1eabn \u0111\u1ebfn s\u1ef1 nh\u1ea7m l\u1eabn m\u1ed9t v\u00e9c t\u01a1 ch\u1ec9 ph\u01b0\u01a1ng c\u1ee7a d l\u00e0 (1,2,3). Nh\u01b0ng v\u1ecb tr\u00ed ph\u00e2n s\u1ed1 cu\u1ed1i \u0111\u00e3 b\u1ecb \u0111\u1ed5i ch\u1ed7 n\u00ean ta c\u1ea7n ph\u1ea3i s\u1eeda l\u1ea1i cho \u0111\u00fang ph\u01b0\u01a1ng tr\u00ecnh d\u01b0\u1edbi d\u1ea1ng (x\u20131)\/1 = (y\u20132)\/2 = (z\u20132)\/ \u20133 th\u00ec m\u1ed9t v\u00e9c t\u01a1 ch\u1ec9 ph\u01b0\u01a1ng c\u1ee7a d l\u00e0 (1,2, \u20133) m\u1edbi l\u00e0 ch\u00ednh x\u00e1c, n\u1ebfu kh\u00f4ng s\u1ebd d\u1eabn \u0111\u1ebfn \u0111\u1ed5i sang ph\u01b0\u01a1ng tr\u00ecnh tham s\u1ed1 sai v\u00e0 c\u00e1c t\u00ednh to\u00e1n sau n\u00e0y s\u1ebd sai k\u1ebft qu\u1ea3.<\/p>\n","protected":false},"excerpt":{"rendered":"

Th\u1ea1c s\u0129 Nguy\u1ec5n V\u0169 Minh (Bi\u00ean H\u00f2a, \u0110\u1ed3ng Nai) ch\u1ec9 ra m\u1ed9t s\u1ed1 l\u1ed7i c\u01a1 b\u1ea3n th\u00ed sinh c\u1ea7n bi\u1ebft \u0111\u1ec3 tr\u00e1nh m\u1ea5t \u0111i\u1ec3m khi l\u00e0m \u0111\u1ec1 th\u00ec m\u00f4n To\u00e1n THPT qu\u1ed1c gia. Trong \u0111\u1ec1 thi THPT qu\u1ed1c gia m\u00f4n To\u00e1n, c\u00f3 r\u1ea5t nhi\u1ec1u nh\u1eefng l\u1ed7i c\u00e1c b\u1ea1n th\u00ed sinh th\u01b0\u1eddng g\u1eb7p ph\u1ea3i d\u1eabn t\u1edbi […]<\/p>\n","protected":false},"author":3,"featured_media":25313,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_mi_skip_tracking":false,"tdm_status":"","tdm_grid_status":""},"categories":[14,157],"tags":[],"yoast_head":"\n