tim x |x+2|+|x+4|+|x+6|=27
tim x
a,3/8=6/x ; b,1/9=x/27
c,4/x=8/6 ; d,3/x-5=-4/x+2
\(a,\dfrac{3}{8}=\dfrac{6}{x}\\ \Rightarrow x=6:\dfrac{3}{8}\\ \Rightarrow x=16\\ b,\dfrac{1}{9}=\dfrac{x}{27}\\ \Rightarrow x=\dfrac{1}{9}.27\\ \Rightarrow x=3\\ c,\dfrac{4}{x}=\dfrac{8}{6}\\ \Rightarrow x=4:\dfrac{4}{3}\\ \Rightarrow x=3\\ d,\dfrac{3}{x-5}=\dfrac{-4}{x+2}\\ \Rightarrow3\left(x+2\right)=-4\left(x-5\right)\\ \Rightarrow3x+6=-4x+20\\ \Rightarrow3x+6+4x-20=0\\ \Rightarrow7x-14=0\\ \Rightarrow7x=14\\ \Rightarrow x=2\)
a: =>6/x=3/8
hay x=16
b: =>x/27=1/9
nên x=3
c: =>4/x=4/3
nên x=3
d: =>3/x-5=-4/x+2
=>3x+2=-4x+20
=>7x=18
hay x=18/7
tim x,y e N a) 2^1-x nhan 3^y = 6^x
b) 4^x = 16^y v 27^x = 9^y+2
minh can gap nha cac ban giup minh nha !!!!!
cau 1.tim x
a)15-|x-4|=6
b)-30+|25-x|=-1
c)x-(12-25)=-8
d) (x-29)-(17-38)=-9
cau 2.tim so nguyen x
a,22-(-x)=12
b,(x+5)+(x-9)=x+2
c,(27-x)+(15+x)=x-24
cho \(\frac{x}{-6}=\frac{y}{4}=\frac{z}{\frac{-1}{2}}\)và 4x+y-2z=27 tim x
Áp dụng tính chất dãy tỉ số bằng nhau, ta có:
\(\frac{x}{-6}=\frac{y}{4}=\frac{z}{-\frac{1}{2}}\)\(=\frac{4x+y-2z}{-6.4+4-\left(-\frac{1}{2}.2\right)}\)\(=\frac{27}{-24+4+1}=\frac{27}{-19}\)
\(\frac{x}{-6}=\frac{-27}{19}\)\(=>x=\frac{\left(-27\right).\left(-6\right)}{19}=\frac{162}{19}\)
Ta có:
\(\frac{x}{-6}\)=\(\frac{4x}{-24}\)
\(\frac{z}{\frac{-1}{2}}\)=\(\frac{2z}{-1}\)
Theo tính chất của dãy tỉ số = nhau:
\(\frac{4x}{-24}\)= \(\frac{y}{4}\)=\(\frac{2z}{-1}\)= \(\frac{4x+y-2z}{-24+4-\left(-1\right)}\)= \(\frac{-27}{19}\)
\(\frac{x}{-6}\)= \(\frac{-27}{19}\)nên x= \(\frac{162}{19}\)= \(8\frac{10}{19}\)
\(\frac{y}{4}\)= \(\frac{-27}{19}\)nên y= \(\frac{-108}{19}\)=\(-5\frac{13}{19}\)
\(\frac{z}{-\frac{1}{2}}\)= \(\frac{-27}{19}\)nên z= \(\frac{27}{38}\)
4)Tinh GTBT
a)x^3 + 12x^2 + 48x + 64 khi x=6
b)x^3 - 6x^2 + 12x - 8 khi x=22
5)Tim x
a) (x+9)^3 = 27
b)8 - 12x - x^3 + 6x^2 = -64
Bài 4:
a, \(x^3+12x^2+48x+64=x^3+4x^2+8x^2+32x+16x+64\)
\(=x^2.\left(x+4\right)+8x.\left(x+4\right)+16.\left(x+4\right)\)
\(=\left(x+4\right).\left(x^2+8x+16\right)=\left(x+4\right).\left(x^2+4x+4x+16\right)\)
\(=\left(x+4\right).\left(x+4\right)^2=\left(x+4\right)^3\)(1)
Thay \(x=6\) vào (1) ta được:
\(\left(6+4\right)^3=10^3=1000\)
Vậy...........
b, \(x^3-6x^2+12x-8=x^3-2x^2-4x^2+8x+4x-8\)
\(=x^2.\left(x-2\right)-4x.\left(x-2\right)+4.\left(x-2\right)\)
\(=\left(x-2\right).\left(x^2-4x+4\right)=\left(x-2\right).\left(x^2-2x-2x+4\right)\)
\(=\left(x-2\right).\left(x-2\right)^2=\left(x-2\right)^3\)(2)
Thay \(x=22\) vào (2) ta được:
\(\left(22-2\right)^3=20^3=8000\)
Vậy.............
Chúc bạn học tốt!!!
Bài 2:
a, \(\left(x+9\right)^3=27=3^3\)
\(\Rightarrow x+9=3\Rightarrow x=-6\)
Vậy.........
b, \(8-12x-x^3+6x^2=-64\)
\(\Rightarrow-\left(x^3-6x^2+12x-8\right)=-64\)
\(\Rightarrow x^3-2x^2-4x^2+8x+4x-8=64\)
\(\Rightarrow x^2.\left(x-2\right)-4x.\left(x-2\right)+4.\left(x-2\right)=64\)
\(\Rightarrow\left(x-2\right).\left(x^2-4x+4\right)=64\)
\(\Rightarrow\left(x-2\right).\left(x^2-2x-2x+4\right)=64\)
\(\Rightarrow\left(x-2\right).\left(x-2\right)^2=64\)
\(\Rightarrow\left(x-2\right)^3=4^3\Rightarrow x-2=4\Rightarrow x=6\)
Vậy............
Chúc bạn học tốt!!!
4. Tính giá trị biểu thức
a) x3 + 12x2 + 48x + 64 khi x = 6
Ta có:
x3 + 12x2 + 48x + 64 =
= (x3 + 64) + (12x2 + 48x)
= (x3 + 43) + 12x(x + 4)
= (x + 4)(x2 - 4x + 42) + 12x(x + 4)
= (x + 4)(x2 - 4x + 16 +12x)
= (x + 4)(x2 + 8x + 16)
= (x + 4)(x + 4)2
= (x + 4)3
Thế x = 6 vào biểu thức vừa tìm, ta được:
(x + 4)3 = (6 + 4)3 = 103 = 1000
Vậy 1000 là giá trị của biểu thức x3 + 12x2 + 48x + 64 khi x = 6.
b) x3 - 6x2 + 12x - 8 khi x = 22
Ta có:
x3 - 6x2 + 12x - 8 =
= (x3 - 8) - (6x2 - 12x)
= (x3 - 23) - 6x(x - 2)
= (x - 2)(x2 + 2x + 22) - 6x(x - 2)
= (x - 2)(x2 + 2x + 4 - 6x)
= (x - 2)(x2 - 4x + 4)
= (x - 2)(x - 2)2
= (x - 2)3
Thế x = 22 vào biểu thức vừa tìm, ta được:
(x - 2)3 = (22 - 2)3 = 203 = 8000
Vậy 8000 là giá trị của biểu thức x3 - 6x2 + 12x - 8 khi x = 22.
5. Tìm x a) (x + 9)3 = 27 \(\Leftrightarrow\) (x + 9)3 = 33 \(\Leftrightarrow\) x + 9 = 3 \(\Leftrightarrow\) x = - 6 Vậy x = -6 b) 8 - 12x - x3 + 6x2 = -64 \(\Leftrightarrow\) (8 - x3) - (12x - 6x2) = -64 \(\Leftrightarrow\) (23 - x3) - 6x(2 - x) = -64 \(\Leftrightarrow\) (2 - x)(22 + 2x + x2) - 6x(2 - x) = -64 \(\Leftrightarrow\) (2 - x)(4 + 2x + x2 - 6x) = -64 \(\Leftrightarrow\) (2 - x)(x2 - 4x + 4) = -64 \(\Leftrightarrow\) -(x - 2)(x - 2)2 = -64 \(\Leftrightarrow\) -(x - 2)3 = -43 \(\Leftrightarrow\) x - 2 = 4 \(\Leftrightarrow\) x = 6 Vậy x = 6
Tim x biet
x-(-25-17-2x)=6+x
45-/-27-(-25)-x/=7+27
1, 7x+6(3-x)=27-20+73
2,6x-5(x-7)=(27-514)-486-73)
3,2x-6=3(x-5)+25+27-15-17
4, 4(x-5)-3(x+5)=2579-2578
5,/x-5/-7(x+4)=5-7x
6,3/x+4/-2(x-1)=7-2x
7, 2/x-6/+7x-2=/x-6/+7x
8,/x+8/+5(x-2)=5x-10:2
9, /x+2/-6(x-4)=20-6x
1: Ta có: 7x+6(3-x)=27-20+73
\(\Leftrightarrow7x+18-6x=80\)
\(\Leftrightarrow x=80-18=62\)
Vậy: x=62
2: Ta có: \(6x-5\left(x-7\right)=\left(27-514\right)-486-73\)
\(\Leftrightarrow6x-5x+35=27-514-486-73\)
\(\Leftrightarrow x+35=-1046\)
\(\Leftrightarrow x=-1081\)
Vậy: x=-1081
Tim X
3) -12 + (2x – 9) + x= 0
4) 11 + (15 - x) = 1
5) 4 - (27 - 3) = x - (13 - 4)
6) 8 - (x - 10) = 23 - (- 4 +12)
7) 105 – 5(10 – 5x) = -20
8) (x -1)(8-2x)(3x+123) = 0
9) (x2 - 25)(x+ 10) = 0
10) x(x2+5) =
3) \(-12+2x-9+x=0\\ -21+3x=0\\ 3x=21\\ x=7\)
4)
\(11+\left(15-x\right)=1\)
\(15-x=1-11\)
\(15-x=-10\)
\(x=15-\left(-10\right)\)
\(x=25\)
5)
\(4-\left(27-3\right)=x-\left(13-4\right)\)
\(4-24=x-9\)
\(x-9=-20\)
\(x=-20+9\)
\(x=-11\)
\(3.-12+\left(2x-9\right)+x=0.\)
\(\Leftrightarrow-12+2x-9+x=0.\Leftrightarrow3x=21.\Leftrightarrow x=7.\)
Vậy \(x=7.\)
\(4.11+\left(15-x\right)=1.\Leftrightarrow11+15-x=1.\Leftrightarrow26-x=1.\Leftrightarrow x=25.\)
Vậy \(x=25.\)
\(5.4-\left(27-3\right)=x-\left(13-4\right).\Leftrightarrow4-24=x-9.\Leftrightarrow-20=x-9.\Leftrightarrow x=-11.\)
Vậy \(x=-11.\)
\(6.8-\left(x-10\right)=23-\left(-4+12\right).\Leftrightarrow8-x+10=23-8.\Leftrightarrow18-x=15.\Leftrightarrow x=3.\)
Vậy \(x=3.\)
\(7.105-5\left(10-5x\right)=-20.\Leftrightarrow105-50+25x=-20.\Leftrightarrow25x=-75.\Leftrightarrow x=-3.\)
Vậy \(x=-3.\)
\(8.\left(x-1\right)\left(8-2x\right)\left(3x+123\right)=0.\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=0.\\8-2x=0.\\3x+123=0.\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1.\\x=4.\\x=-41.\end{matrix}\right.\)
Vậy \(x\in\left\{1;4;-41\right\}.\)
\(9.\left(x^2-25\right)\left(x+10\right)=0.\)
\(\Leftrightarrow\left(x-5\right)\left(x+5\right)\left(x+10\right)=0.\)
\(\Leftrightarrow\left[{}\begin{matrix}x-5=0.\\x+5=0.\\x+10=0.\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=5.\\x=-5.\\x=-10.\end{matrix}\right.\)
Vậy \(x\in\left\{5;-5;-10\right\}.\)
\(10.x\left(x^2+5\right)=0.\Leftrightarrow x=0.\)
tim x,biet
a)x-6=35:7+42:6
b)x-54:27=42-26:2
c)36:x+81:x=130:10
a. x -6 = 35 : 7 + 42 : 6
=> x - 6 = 5 + 7
=> x -6 = 12
=> x = 12 + 6
=> x = 18
Các câu sau tương tự, bạn học tốt nha! .-.
a)x-6=5+7
x-6=12
x=6.
b)x-2=42-13
x-2=29
x=29+2
x=31
c)(36+81):x=13
117:x=13
x=117:13
x=9.
a)x-6=35:7+42:6
x-6=5+7
x-6=12
x=12:6
x=2
Vậy x=2