B\u00e0i 74 (trang 127 sgk Gi\u1ea3i T\u00edch 12 n\u00e2ng cao):<\/b>\u00a0<\/span><\/p>\n Gi\u1ea3i c\u00e1c Ph\u01b0\u01a1ng tr\u00ecnh<\/p>\n a) log2<\/sub>(3-x)+log2<\/sub>(1-x)=3<\/p>\n b) log2<\/sub>(9-2x<\/sup>)=10lg\u2061(3-x)<\/sup><\/p>\n c) 7lgx<\/sup>-5lgx+1<\/sup>=3.5lgx-1<\/sup>-13.7lgx-1<\/sup><\/p>\n d) 6x<\/sup>+6x+1<\/sup>=2x<\/sup>+2x+1<\/sup>+2x+2<\/sup><\/p>\n L\u1eddi gi\u1ea3i:<\/b><\/p>\n a) \u0110i\u1ec1u ki\u1ec7n: x < 1. Ph\u01b0\u01a1ng tr\u00ecnh \u0111\u00e3 cho t\u01b0\u01a1ng d\u01b0\u01a1ng v\u1edbi<\/p>\n (3-x)(1-x)=23<\/sup>\u00a0<=> x2<\/sup>-4x-5=0<\/p>\n <\/p>\n V\u1eady Ph\u01b0\u01a1ng tr\u00ecnh c\u00f3 nghi\u1ec7m x= -1<\/p>\n b) \u0110i\u1ec1u ki\u1ec7n: x < 3. Ph\u01b0\u01a1ng tr\u00ecnh \u0111\u00e3 cho t\u01b0\u01a1ng d\u01b0\u01a1ng v\u1edbi<\/p>\n 9-2x<\/sup>=23-x<\/sup>\u00a0<=> (2x<\/sup>)2<\/sup>-9.2x<\/sup>+8=0<\/p>\n <\/p>\n V\u1eady: Ph\u01b0\u01a1ng tr\u00ecnh c\u00f3 nghi\u1ec7m x = 0<\/p>\n c) 7lgx<\/sup>+13.7lgx-1<\/sup>=3.5lg\u2061x-1<\/sup>+5lgx+1<\/sup><\/p>\n <=> 20.7lgx-1<\/sup>=28.7lgx+1<\/sup><=> (7\/5)lgx-1<\/sup>=7\/5<\/p>\n <=> lgx \u2013 1 = 1 <=> lgx = 2 <=> x = 100<\/p>\n d) 6x<\/sup>+6x+1<\/sup>=2x<\/sup>+2x<\/sup>+1)+2x+2<\/sup>\u00a0<=> 7.6x<\/sup>=7.2x<\/sup>\u00a0<=> 3x<\/sup>\u00a01 <=> x = 0<\/p>\n B\u00e0i 75 (trang 127 sgk Gi\u1ea3i T\u00edch 12 n\u00e2ng cao):<\/b>\u00a0<\/span><\/p>\n Gi\u1ea3i c\u00e1c Ph\u01b0\u01a1ng tr\u00ecnh<\/p>\n <\/p>\n L\u1eddi gi\u1ea3i:<\/b><\/p>\n a) \u0110i\u1ec1u ki\u1ec7n: 3x<\/sup>-1 > 0<\/p>\n <=> log3<\/sub>(3x<\/sup>-1) (1+log3<\/sub>(3x<\/sup>-1) )=12<\/p>\n <=> log3<\/sub>2\u2061(3x<\/sup>-1)+log3<\/sub>(3x<\/sup>-1)-12=0<\/p>\n <\/p>\n b) \u0110i\u1ec1u ki\u1ec7n: 0 < x-1 \u2260 1<\/p>\n <\/p>\n c) \u0110i\u1ec1u ki\u1ec7n: x \u2264 -1<\/p>\n \u0110\u1eb7t t=log2<\/sub>(-x) ta \u0111\u01b0\u1ee3c.<\/p>\n <\/p>\n <\/p>\n B\u00e0i 76 (trang 127 sgk Gi\u1ea3i T\u00edch 12 n\u00e2ng cao):<\/b>\u00a0<\/span><\/p>\n Gi\u1ea3i c\u00e1c Ph\u01b0\u01a1ng tr\u00ecnh:<\/p>\n <\/p>\n L\u1eddi gi\u1ea3i:<\/b><\/p>\n a) \u0110i\u1ec1u ki\u1ec7n x \u2260 0. Ph\u01b0\u01a1ng tr\u00ecnh t\u01b0\u01a1ng \u0111\u01b0\u01a1ng v\u1edbi:<\/p>\n <\/p>\n Ta \u0111\u01b0\u1ee3c Ph\u01b0\u01a1ng tr\u00ecnh:<\/p>\n <\/p>\n b) \u0110i\u1ec1u ki\u1ec7n x > 0. Ta \u0111\u01b0\u1ee3c Ph\u01b0\u01a1ng tr\u00ecnh:<\/p>\n <\/p>\n c) \u0110i\u1ec1u ki\u1ec7n log2<\/sub>\u2061x \u2265 0. Ph\u01b0\u01a1ng tr\u00ecnh t\u01b0\u01a1ng d\u01b0\u01a1ng v\u1edbi:<\/p>\n <\/p>\n d) \u0110i\u1ec1u ki\u1ec7n x > 0, ta c\u00f3:<\/p>\n <\/p>\n Ph\u01b0\u01a1ng t\u00ecnh \u0111\u00e3 cho t\u01b0\u01a1ng \u0111\u01b0\u01a1ng v\u1edbi ph\u01b0\u01a1ng tr\u00ecnh:<\/p>\n <\/p>\n B\u00e0i 77 (trang 127 sgk Gi\u1ea3i T\u00edch 12 n\u00e2ng cao):<\/b>\u00a0<\/span><\/p>\n Gi\u1ea3i c\u00e1c Ph\u01b0\u01a1ng tr\u00ecnh:<\/p>\n a) 2sin2\u2061x<\/sup>\u00a0+4.2cos2\u2061x<\/sup>\u00a0=6 \u00a0\u00a0\u00a0 b) 43+2cos2x<\/sup>-7.41+cos2x<\/sup>=41\/2<\/sup><\/p>\n L\u1eddi gi\u1ea3i:<\/b><\/p>\n a) 2sin2\u2061x<\/sup>\u00a0+4.2cos2\u2061x<\/sup>\u00a0=6 <=> 2sin2\u2061x<\/sup>\u00a0+4.21-sin2\u2061x<\/sup>=6 <=> 22 sin2\u2061x<\/sup>-6sin2\u2061x<\/sup>\u00a0+8=0<\/p>\n \u0110\u1eb7t t=2sin2\u2061x<\/sup>\u00a0(t > 0)<\/p>\n Ta \u0111\u01b0\u1ee3c:<\/p>\n <\/p>\n V\u1edbi t=2 => 2sin2\u2061x<\/sup>\u00a0=2 <=> sin2<\/sup>\u2061x=1 <=> cos\u20612<\/sup>x=0 <=> cosx = 0 <=> x=\u03c0\/2+k \u03c0 (k \u2208Z)<\/p>\n V\u1edbi t = 4 => 2sin2\u2061x<\/sup>\u00a0=4 <=> sin2<\/sup>\u2061x=2. PT v\u00f4 nghi\u1ec7m.<\/p>\n V\u1eady Ph\u01b0\u01a1ng tr\u00ecnh c\u00f3 c\u00f3 nghi\u1ec7m: x=\u03c0\/2+k \u03c0(k \u2208Z)<\/p>\n B\u00e0i 78 (trang 127 sgk Gi\u1ea3i T\u00edch 12 n\u00e2ng cao):<\/b>\u00a0<\/span><\/p>\n Gi\u1ea3i c\u00e1c ph\u01b0\u01a1ng tr\u00ecnh:<\/p>\n <\/p>\n L\u1eddi gi\u1ea3i:<\/b><\/p>\n a) D\u1ec5 th\u1ea5y x = -1 l\u00e0 nghi\u1ec7m. ta ch\u1ee9ng minh x = -1 l\u00e0 nghi\u1ec7m duy nh\u1ea5t.<\/p>\n Th\u1eadt v\u1eady:<\/p>\n <\/p>\n VP + x + 4 < -2 + 3 => VT > VP<\/p>\n Ph\u01b0\u01a1ng tr\u00ecnh kh\u00f4ng th\u1ecfa m\u00e3n v\u1edbi x < -1<\/p>\n <\/p>\n VP=x+4 > -1 + 4 = 3 => VT < VP<\/p>\n Ph\u01b0\u01a1ng tr\u00ecnh v\u00f4 nghi\u1ec7m v\u1edbi x > -1<\/p>\n V\u1eady Ph\u01b0\u01a1ng tr\u00ecnh c\u00f3 nghi\u1ec7m duy nh\u1ea5t x = -1<\/p>\n b) D\u1ec5 th\u1ea5y: x = 2 l\u00e0 nghi\u1ec7m c\u1ee7a Ph\u01b0\u01a1ng tr\u00ecnh. Ta ch\u1ee9ng minh x =2 l\u00e0 nghi\u1ec7m duy nh\u1ea5t. th\u1eadt v\u1eady:<\/p>\n <\/p>\n T\u01b0\u01a1ng t\u1ef1:<\/p>\n <\/p>\n V\u1eady: Ph\u01b0\u01a1ng tr\u00ecnh c\u00f3 nghi\u1ec7m duy nh\u1ea5t l\u00e0 x = 2.<\/p>\n B\u00e0i 79 (trang 127 sgk Gi\u1ea3i T\u00edch 12 n\u00e2ng cao):<\/b>\u00a0<\/span><\/p>\n Gi\u1ea3i c\u00e1c h\u1ec7 Ph\u01b0\u01a1ng tr\u00ecnh:<\/p>\n <\/p>\n L\u1eddi gi\u1ea3i:<\/b><\/p>\n <\/div>\n","protected":false},"excerpt":{"rendered":" B\u00e0i 74 (trang 127 sgk Gi\u1ea3i T\u00edch 12 n\u00e2ng cao):\u00a0 Gi\u1ea3i c\u00e1c Ph\u01b0\u01a1ng tr\u00ecnh a) log2(3-x)+log2(1-x)=3 b) log2(9-2x)=10lg\u2061(3-x) c) 7lgx-5lgx+1=3.5lgx-1-13.7lgx-1 d) 6x+6x+1=2x+2x+1+2x+2 L\u1eddi gi\u1ea3i: a) \u0110i\u1ec1u ki\u1ec7n: x < 1. Ph\u01b0\u01a1ng tr\u00ecnh \u0111\u00e3 cho t\u01b0\u01a1ng d\u01b0\u01a1ng v\u1edbi (3-x)(1-x)=23\u00a0<=> x2-4x-5=0 V\u1eady Ph\u01b0\u01a1ng tr\u00ecnh c\u00f3 nghi\u1ec7m x= -1 b) \u0110i\u1ec1u ki\u1ec7n: x < 3. Ph\u01b0\u01a1ng tr\u00ecnh \u0111\u00e3 […]<\/p>\n","protected":false},"author":3,"featured_media":23360,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_mi_skip_tracking":false,"tdm_status":"","tdm_grid_status":""},"categories":[1302],"tags":[1392,1393],"yoast_head":"\n