shestakov-all-gdz-2004 (546287), страница 15
Текст из файла (страница 15)
Ответ: x = 2.⎛1⎞⎝ ⎠−x2.5.B09. а) 351− x = ⎜ ⎟ ⋅ 7 x ; 351− x = 5 x 7 x ; 351− x = 35 x ; 1 − x = x ;511.Ответ: x = .22−xб) 633 − x = ⎛ 1 ⎞ ⋅ 9 x ; 633− x = 7 x ⋅ 9 x ; 633− x = 63x ; 3 − x = x ;⎜ ⎟⎝7⎠332 x = 3; x = . Ответ: .22⎧⎪ 4 ⋅11x + y = 48 ⎧⎪4t + y = 48⎧⎪ 4(27 − 4 y ) + y = 482.5.B10. а) ⎨ x; ⎨ x; ⎨ x;⎪⎩11 + 4 y = 27 ⎪⎩11 + 4 y = 27 ⎪⎩11 = 27 − 4 y4(27 − 4 y ) + y = 48 ; 108 − 16 y + y = 48 ; −15 y = −60 ;1 = 2 x; x =y = 4 ; 11x = 27 − 4 ⋅ 4 ; 11x = 11 ⇒ x = 1 . Ответ: x = 1, y = 4.x⎪⎧3 ⋅ 5 + y = 78б) ⎨x⎪⎩5 − 3 y = 16x⎪⎧3 ⋅ 5 + y = 78; ⎨x⎪⎩5 = 16 + 3 y⎧⎪3(16 + 3 y ) + y = 78;x⎪⎩5 = 16 + 3 y; ⎨48 + 9 y + y = 78 ; 10 y = 30 ; y = 3 ; 5x = 16 + 3 ⋅ 3 ; x = 2 .Ответ: x = 2, y = 3.xy⎪⎧2 − 4 ⋅ 2 = −622.5.B11.
а) ⎨xy⎪⎩3 ⋅ 2 + 4 ⋅ 2 = 70⎧⎪2 x − 70 + 3 ⋅ 2 x = −62; ⎨yx⎪⎩4 ⋅ 2 = 70 ⋅ 3 ⋅ 2; 2x − 8 + 3 ⋅ 2x = 0 ;4 ⋅ 2 x = 8 ; 2 x = 2 ; x = 1 ; 4 ⋅ 2 y = 70 − 3 ⋅ 2 ; 2 y = 16 ; y = 4. Ответ: x = 1, y = 4.xy⎪⎧3 + 3 ⋅ 3 = 54б) ⎨xx⎪⎧3 + 4 ⋅ 3 − 81 = 54; ⎨xyxy⎪⎩4 ⋅ 3 − 3 ⋅ 3 = 81 ⎪⎩4 ⋅ 3 − 81 = 3 ⋅ 3; 5 ⋅ 3x = 135 ; 3x = 127 ; x = 3 ;3 ⋅ 3 y = 4 ⋅ 3 y − 81 ; 3 y = 9 ; y = 2 . Ответ: x = 3, y = 2.xy⎪⎧4 + 3 ⋅ 4 = 28; 41+ y + 3 ⋅ 4 y = 28 ; 4 ⋅ 4 y + 3 ⋅ 4 y = 28 ; 4 y = 4 ; y = 1 ;⎪⎩ x − y = 12.5.B12. а) ⎨x = 1 + y ⇒ x = 2 . Ответ: x = 2, y = 1.⎧⎪3x − 4 ⋅ 3 y = 69 3+ y; 3 − 4 ⋅ 3 y = 69 ; 27 ⋅ 3 y − 4 ⋅ 3 y = 69 ;б) ⎨⎪⎩ x − y = 33 y = 3 ; y = 1 ; x = 3 + y ⇒ x = 4 .
Ответ: x = 4, y = 1.Уровень С.⎛ 2⎞−x5x5x−36 x −18= 2 2 ; 26 x −18 − 3 = 2 2 ;2.5.C01. а) 0,125 ⋅ 43 x − 9 = ⎜⎜⎟⎟ ; 2 ⋅ 28⎝⎠113571x ; x = 21 ; x = 3 ; x = 6 .222−x3x173⎛⎞2б) 0, 25 ⋅ 45 x −16 = ⎜; 210 x − 32 − 2 = 2 2 ; 10 x − 34 = x ;x = 34 ; x = 4 .⎟22⎜ 4 ⎟⎝⎠6 x − 21 =2.5.C02. а) 43 xПусть 223 x2 + x23x + x2+x− 28 = −3 ⋅ 81x2 + x3; 3 ⋅ 23 x2+x+ 26 x2+2x− 28 = 0 .2= t , тогда t + 3t − 28 = 0 ; t1 = −7, t2 = 4не может равняться −73 x2 + x2= 4 ; 23 x + x = 22 ; 3x 2 + x − 2 = 0 ; D = 1 + 24 = 25 ;−1 ± 52; x1 = −1 , x2 = .x=632б) 92 x2+2x− 15 = −2 ⋅ 91x + x9 22Пусть1x2 + x21x2 + x2; 92 x2+x+ 2⋅91x2 + x2− 15 = 0 .= t , тогда t 2 + 2t − 15 = 0 ; t1 = −5, t2 = 3 ;1x2 + x2= 32 x12 x 2 + x − 1 = 0 ; D = 1 + 8 = 9 ; x1 = −1, x2 = ;29не может равняться −5 ; 92+x= 31 ;1t2.5.C03.
а) 52 x + 5−2 x = 2 . Пусть 52 x = t > 0 ; t + = 2 ; t 2 − 2t + 1 = 0 ;t1 = t2 = 1 ; 52 x = 50 ; 2 x = 0 ; x = 0 .1tб) 62 x + 6−2 x = 2 ; 62 x = t ; t + = 2 ; t 2 − 2t + 1 = 0 ; t = 1 ; x = 0 .2.5.C04. а) 8x −1 − 6 ⋅ 8− x + 2 − 2 = 0 ; 8x-1-48·8-x+1-2=0; 8x-1=t>0; t-48-2=0;tt2-2t-48=0; t1=8, t2=-; 8x-1 не может равняться –8; 8x-1=81; x-1=1; x=2.б) 3x+5-6·3-x-4+3=0; 3x+5-18·3x-5+3=0; 3x+5=t>0; t-18+3=0; t2+3t-18=0;tt1=3, t2=-6; 3x+5 не может равняться –6; 3x+5=31; x+5=1; x=-4.2.5.C05. а) 9x-24· 332x33x-243 383x⋅ 32x −32x 3−2=3·3-x; 32x-24· 3 2-3·3-x=0;-3·3-x=0; Домножим обе части уравнения на 3x ≠ 0 ;·31,5x-3=0; 31,5x=t; t2-83·t-3=0; D=10 264100=();+ 12(3 =3338 10+3 =3 3 , t = 4 − 5 =- 1 <0, t 3x; 31,5x=31,5 ; x=1.t1= 322≠2333xб) 16 -31·1143x −52 23x-x4x=2 ;2 -31⋅ 2 24 2-2-x=0;5x5x31961 + 12833 2t -1=0; D==() ;32324 24 231335x1+4242 = 8 = 4 2 ; 2 2 = 22 2 ; x=1.t1=223125x-⋅ 2 2 -1=0; 2 2 = t > 0 ; t2-4645 − 3 x = 3 168 + x ; 215-9x= 2 32.5.C06.
а)311313x= ; x= .3331279 − 5 x = 3 97 + x ; 3б)27 −15 x214 + 2 x3=3(8 + x ); 15-9x=44·8+ x33; 81-45x=28+4x; 49x=53; x=53.492.5.C07.а)14x4 x + 24 − 4 x (4 x + 3)= x;=0;(4 x + 3)(4 x + 24)4 + 3 4 + 24x42x+2·4x-24=0; 4x=t>0; t2+2t-24=0; t1=4, t2=-6;4x не может равняться –6; 4x=4, x=1.б)13x=; 3x+18=32x+4·3x; 32x+3·3x-18=0; 3x=t>0;3x + 4 3x + 18t1=3, t2=-6; 3x не может равняться –6; 3x=3, x=1.2.5.C08.xa)x1⎛ 1 ⎞2 1 −22−x; ⋅ 5 + 5− x − = 0 ;⎜⎟ +5 =5⎝ 5 ⎠25 52525·5-x+5· 515t1= , t2=-−x2-2=0; 5−x2= t > 0 ; 25t2+5t-2=0; t2+xt 2=0;5 25x−−22x; 5 2 не может равняться - ; 5 2 = 5−1 ; = 1 ; x=2.552xxx−4⎛ 1 ⎞1 -x 4 − 2 112 4−x2⎜⎟ + 6 = ; 6 + · 6 - =0; 6 = t > 0 ; t + t − = 0 ;3⎝ 6 ⎠4343 44 5− +1162533; t1= 3 3 = ; t2=- ; 6-x не может равняться - ;D= + 1 =269922б)6−x2= 6−1 ;x= 1 ; x=2.2⎧⎪4 x ⋅ 5 y = 202.5.C09.
⎨ x y −1;⎪⎩16 ⋅ 5 = 165-y=⎧⎪4 x ⋅ 5 y = 20;⎨ 2 x y −1⎪⎩4 ⋅ 5 = 16⎧ x 20⎪⎪4 = 5 y400 − y;⋅ 5 = 16 ;⎨ 25⎪ 20 ⋅ 5 y −1 = 16⎪⎩ 52 y16 1 -y -120= ; 5 =5 ; y=1; 4x== 4 ; x=1. Ответ: x=1, y=1.80 55115⎧ y 10⎪⎪2 = 5 x10; 5x=5; x=1; 2y= ; y=1. Ответ: x=1, y=1.⎨ 2x5⋅510⎪= 25⎪⎩ 5 x ⋅ 2xy⎪⎧5 ⋅ 2 = 10б) ⎨ x y −1;⎪⎩25 ⋅ 2 = 25⎧ 64yxy⎪⎧2 − 2 = 12 ⎪ y − 2 = 12; ⎨2;⎪⎩ x + y = 6⎪x = 6 − y⎩2.5.C10. a) ⎨22y+12·2y-64=0; 2y=t; t2+12t-64=0; t1=4, t2=-16;2y не может равняться –16; 2y=4; y=2; x=6-2=4. Ответ: x=4,y=2.⎧ 35xy⎪⎧3 − 3 = −78 ⎪ y − 3 y = −78 2y; ⎨3; 3 -78·3y-243=0; 3y=t>0; t2-78·t-243=0; t1=-3,⎪⎩ x + y = 5⎪x = 5 − y⎩б) ⎨t2=81; 3y=81; y=4; x=5-4=1.
Ответ: x=1, y=4.⎧⎪2 x +1 ⋅ 3 y + 2 = 2 ⎧⎪2 x +1 ⋅ 3x = 2 -x x; ⎨; 2 =3 ; x=0; y=-2.⎪⎩ y = x − 2⎪⎩ x − y = 22.5.C11. a) ⎨Ответ: x = 0, y = –2.x +3y −3x +3x+2⎪⎧3 ⋅ 2 = 3 ⎪⎧3 ⋅ 2 = 3; ⎨;⎪⎩ y = x + 5⎪⎩ x − y = −5б) ⎨3x+2=2-x-2; x+2=0; x=-2; y=3. Ответ: x = –2, y = 3.2.5.C12. а) 32x+1=27+53·3x+32x; 32x(3-1)-53·3x-27=0;2·32x-53·3x-27=0; 3x=t>0; 2t2-53t-27=0; D=2809+8·27=(55)2;t=53 ± 5553 + 551; t1==27, t2=- ≠ 3x; 3x=27;x=3.442б) 52x+1=25+74·5x+2·52x; 3·52x-74·5x-25=0; 5x=t>0;74 − 761= − ≠ 5x; t2=25; 5x=25; x=2.63D=5476+300=5776=(76)2; t1=Уровень D.2.5.D01 a) 121· 13x121· 132x −911(11· 1311· 13x2б) 169· 8 x13(13· 813· 82-143· 11−6x −6x2 − 6-13· 11x-13· 112−9-8· 13x-8· 13-8· 132−5−8)=13(13· 112−102)=8(8· 13x2 − 72= 11x−62− 132-11· 13x2x −92−8;;x2 − 9);; x2-10=0; x= ± 10 .2-13· 8x2 − 7−9-11· 13−10-13· 8 xx −62-143· 13x2 − 9=64· 13x=0; 8=169· 11x2x −9=0; 13xx −6x2 − 6222=169· 11x2 − 9-13· 11x2−92x −9x2 − 9−92−5;x2 − 6);2= 0 ; x -7=0; x= ± 7 .222.5.D02.
a) 81+ x − 8 ⋅ 81- x = 56 ; 64· 8−1+ x -8· 81− x =56;264− 3t = 56 ; t2+7t-8=0; t1=1, t2=-8 ≠ 8− x +1 ;t8− x2+1=t >0;8− x2+1= 80 ; x2-1=0; x= ±1 .11622222б) 51+ x -5· 51− x =20; 25· 5−1+ x -5· 51− x =20; Пусть 51− x =t>0.2225− 5t = 20 ; t2+4t-5=0; t1=1, t2=-5 ≠ 51− x ; 51− x =50; x2=1; x= ± 1.tx +32.5.D03. a) 25252 x +3+ 5 = 0 ; 542=t>0; t -6t+5=0; t1=5, t2=1; 513x+3= ; x1=-2 ; 5244б) 9x +3− 6 ⋅ 52x−2x1=3; 3-4· 3x−2x−20x +32 x +3x +3x +3− 6 ⋅ 52+5 = 0 ;1=5 ; 2 x + 3 =1;340=5 ; x+3=0; x2=-3. Ответ: x1 = −2 , x2 = –3.+3=0; 3x−2=t>0; t2-4t+3=0; t1=3, t2=1; 3x−2=31;x − 2 =1;=3 ; x-2=0;x2=2.
Ответ: x1 = 3, x2 = 2.⎧ 4 y −14 y −1y +3⎧⎪ x 4 y −1 = 8 ⎪ x 3 = 24 y −1 y + 32.4.D04. a) ⎨ y + 3; ⎨ y +3; x 3 =x 4 ;;=34= 16 ⎪ 4⎪⎩ x=2⎩x16y-4=3y+9; 13y=13; y=1; x4-1=8; x=2. Ответ: x = 2, y = 1.⎧ 3 y − 113 11y−311⎪x2 2 = 4; x 2 2 = x y −3 ; y − = y − 3 ;⎨22⎪⎩ x y − 3 = 43 y −11= 16⎪⎧ xб) ⎨ y − 3;=4⎪⎩ x3y-2y=-6+11; y=5; x2=4; x=2. Ответ: x = 2, y = 5.−x+2⎧⎪ x − 22x−4x + 2 − 0,5 y− 26 ⋅ 3x + 2 − 4,5 − 0,5 x = 3− x + 2⎪⎧3=32.5.D05.
a) ⎨9 − 26 ⋅ 3; ⎨;⎪⎩ y = 9 + x⎩⎪ y − x = 9|·3-2+x;32x-4-26·30,5x-2,5-3-x+2=032x-4-26·31,5x-3-1=0; 31,5x-3=t>0; t2-26·t-1=0;3 32628+2676 + 4 ⋅ 27 784 ⎛ 28 ⎞3333 = 54 ; 0>t ≠31,5x-3;D===⎜2⎟ ; t1=22727 ⎝ 3 3 ⎠2⋅3 3271,5x-31,5x-31,533 3=3 3;3=3 ; 1,5x-3=1,5; x=3; y=12. Ответ: x = 3, y = 12.x −1x +1− 0,5 y= 4− x +1 ⎪⎧42 x − 2 + 63 ⋅ 40,5 x − 2 = 4− x +1⎪⎧16 + 63 ⋅ 4; ⎨;⎪⎩ y − x = 6⎩⎪ y = 6 + xб) ⎨43x-3+63·41,5x-3-1=0; 43x+63·41,5x-64=0; 41,5x=t>0; t2+63t-64=0;t1=1, t2=-64 ≠ 41,5x; 41,5x=40; x=0; y=6. Ответ: x = 0, y = 6.2.5.D06. a) 25⎛ 25 ⎞⎜ ⎟⎝ 49 ⎠−3x⎛5⎞+⎜ ⎟⎝7⎠−−3x3x+ 35−3x= 49−3x−3x⎛5⎞−1 = 0 ; ⎜ ⎟⎝7⎠−1 + 5⎛5⎞, 0>t2 ≠ ⎜ ⎟t1=2⎝7⎠−3x.
Разделим на 49−3x;= t > 0 ; t2+t-1=0; D=1+4=5;⎛5⎞; ⎜ ⎟⎝7⎠−3x=5 −135 −1; − = log 5; x= −2x273log 575 −12.1173333б) 49 x − 42 x = 3 ⋅ 36 x . Разделим на 36 x ;633⎛ 7 ⎞x ⎛ 7 ⎞x⎛ 7 ⎞x2⎜ ⎟ − ⎜ ⎟ − 3 = 0 ; ⎜ ⎟ = t > 0 ; t -t-3=0; D=1+12;⎝6⎠ ⎝6⎠⎝6⎠3⎛7⎞⎜ ⎟31 + 131 + 131 + 13 ⎝ 6 ⎠⎛ 7 ⎞ x ⎛ 7 ⎞ x 1 + 13 3t1=, 0>t2 ≠ ⎜ ⎟ ; ⎜ ⎟ =; = log 7; x = 3log.66222x2⎝ ⎠ ⎝ ⎠6232.5.D07. a) 24( x + 3) = − 2 ⋅ 4( x + 4)( x + 2) ;2223134( x + 3)22( x + 4)( x + 2)2+ 2⋅2= ; 24( x + 3) + ⋅ 22( x + 3) − = 0 ;2222332 12( x + 3)22( x + 3)22= t > 0 ; t + t - =0; t1=1, t=- ≠ 2; 22( x + 3) = 20 ;2 222(x+3)2=0; x=–3.22414− 3 ⋅ 9( x + 3)( x +1) ; 34( x + 2) + ⋅ 32( x + 2) − = 0 ;333442 12( x + 2)2= t > 0 ; t + t − = 0 ; t1=1, t2= − ≠ 3;3 332б) 34( x + 2) =32( x + 2)22(x+2)2=0; x+2=0; x=-2.2.5.D08.x⎛ 27 ⎞ ⎛ 4 ⎞x +1⎛3⎞⎜ ⎟⎝2⎠x−2=3x=a) ⎜ ⎟ ⎜ ⎟⎝ 8 ⎠ ⎝9⎠lg 27 ⎛ 3 ⎞ ⎛ 3 ⎞; ⎜ ⎟ ⎜ ⎟lg 9 ⎝ 2 ⎠ ⎝ 2 ⎠−2 x − 2= log9 27 = 1,5 ;3; x-2=1; x=3.2x⎛9⎞ ⎛ 8 ⎞x +1=б) ⎜ ⎟ ⎜ ⎟⎝ 4 ⎠ ⎝ 27 ⎠lg 64 ⎛ 3 ⎞; ⎜ ⎟lg16 ⎝ 2 ⎠2.5.D09.