Bài 1.Tìm x thuộc N, biết:
a) x-26=60
b)2x-12=4
c)52x=520:510
1. Tìm x biết
a. 8x +56 : 14 = 60
b. 52x-3- 2.52 = 52 . 3
c. 41- 2x+1=9
d.32x-4-x0= 8
g) 65-4x+2=20140
i. 120+ 2.(4x-17) =214
a) \(8x+56:14=60\)
\(\Rightarrow8x+4=60\)
\(\Rightarrow8x=56\)
\(\Rightarrow x=\dfrac{56}{8}\)
\(\Rightarrow x=7\)
b) Mình làm rồi nhé !
c) \(41-2^{x+1}=9\)
\(\Rightarrow2^{x+1}=41-9\)
\(\Rightarrow2^{x+1}=32\)
\(\Rightarrow2^{x+1}=2^5\)
\(\Rightarrow x+1=5\)
\(\Rightarrow x=4\)
d) \(3^{2x-4}-x^0=8\)
\(\Rightarrow3^{2x-4}-1=8\)
\(\Rightarrow3^{2x-4}=9\)
\(\Rightarrow3^{2x-4}=3^2\)
\(\Rightarrow2x-4=2\)
\(\Rightarrow2x=6\)
\(\Rightarrow x=3\)
g) \(65-4^{x+2}=2014^0\)
\(\Rightarrow65-4^{x+2}=1\)
\(\Rightarrow4^{x+2}=64\)
\(\Rightarrow4^{x+2}=4^3\)
\(\Rightarrow x+2=3\)
\(\Rightarrow x=1\)
i) \(120+2\left(4x-17\right)=214\)
\(\Rightarrow2\left(4x-17\right)=214-120\)
\(\Rightarrow2\left(4x-17\right)=94\)
\(\Rightarrow4x-17=47\)
\(\Rightarrow4x=47+17\)
\(\Rightarrow4x=64\)
\(\Rightarrow x=16\)
a: \(8x+56:14=60\)
=>8x+4=60
=>8x=60-4=56
=>x=56/8=7
b: \(5^{2x-3}-2\cdot5^2=5^2\cdot3\)
=>\(5^{2x-3}=5^2\cdot3+2\cdot5^2=5^3\)
=>2x-3=3
=>2x=6
=>x=3
c: \(41-2^{x+1}=9\)
=>\(2^{x+1}=41-9=32\)
=>x+1=5
=>x=4
d: \(3^{2x-4}-x^0=8\)
=>\(3^{2x-4}-1=8\)
=>\(3^{2x-4}=8+1=9\)
=>2x-4=2
=>2x=6
=>x=3
g: \(65-4^{x+2}=2014^0\)
=>\(65-4^{x+2}=1\)
=>\(4^{x+2}=65-1=64\)
=>x+2=3
=>x=1
i: 120+2(4x-17)=214
=>2(4x-17)=214-120=94
=>4x-17=94/2=47
=>4x=64
=>\(x=\dfrac{64}{4}=16\)
Tìm x,y biết:
a)3x - y = 13 và 2x + 4y = 60
b)5x + 2y = 69 và 4x = 3y
c)4x - 3y = 42 và 2x = 5y
a) Ta có: \(3x-y=13\) và \(2x-4y=60\)
Mà: \(2\left(x+2y\right)=60\Rightarrow x+2y=30\) (1)
Và: \(3x-y=13\Rightarrow6x-2y=26\) (2)
Cộng (1) với (2) theo vế ta có:
\(\left(x+6x\right)+\left(-2y+2y\right)=30+26\)
\(\Rightarrow7x=56\)
\(\Rightarrow x=8\)
Ta tìm được y:
\(8+2y=30\)
\(\Rightarrow2y=22\)
\(\Rightarrow y=11\)
b) Ta có: \(5x+2y=69\) và \(4x=3y\Rightarrow4x-3y=0\)
Mà: \(5x+2y=69\Rightarrow15x+6y=207\) (1)
\(4x-3y=0\Rightarrow8x-6y=0\) (2)
Cộng (1) và (2) theo vế ta có:
\(\left(15x+8x\right)+\left(6y-6y\right)=207+0\)
\(\Rightarrow23x=207\)
\(\Rightarrow x=\dfrac{207}{23}\)
\(\Rightarrow x=9\)
Ta tìm được y:
\(4\cdot9=3\cdot y\)
\(\Rightarrow3y=36\)
\(\Rightarrow y=\dfrac{36}{3}\)
\(\Rightarrow y=12\)
Tìm số tự nhiên x,biết:
a)58 + 7x = 100
b) ( x –12):12=12
c) x -56 : 4= 16
d) 101 +(36 –4x) =105
e) 2(x-51) = 2.23+ 20
f) 10 -(x –3): 2 = 72–110
g) 2x –49 = 5.32h) [(8x -12) : 4].33= 36
i) 52x –3–2 . 52= 52. 3 k) (x3–7) : 4 = 5
a: 7x+58=100
nên 7x=42
hay x=6
c: x-56:x=16
nên x-14=16
hay x=30
c)x - 56 : 4 = 16
x - 56 = 16 : 4
x- 56 = 4
x =4 + 56
x = 60
d)101 + (36 - 4x) = 105
(36- 4x ) = 105 - 101
36 - 4x = 4
4x = 36 - 4
4x = 32
x = 32:4
x = 8
a) 58 + 7x = 100
7x = 100 - 58
7x = 42
x = 42 : 7
x = 6
b) (x - 12) : 12 = 12
x - 12 = 12 . 12
x - 12 = 144
x = 144 + 12
x = 156
Bài 9: Tìm x, biết:
a)|-2x+1,5|=1/4
b)3/2-|1 1/4+3x|=1/4
c)|4x-1| - |3x-1/2|=0
d)|x-1|-2x=1/2
Giúp mình với mình đang cần gấp
\(|-2x+1,5|=\dfrac{1}{4}\Rightarrow-2x+1,5=\pm\dfrac{1}{4}\)
\(-2x+1,5=\dfrac{1}{4}\Rightarrow-2x=1,5-0,25\Rightarrow-2x=1,25\Rightarrow x=1,25:\left(-2\right)\Rightarrow x=...\)
\(-2x+1,5=-\dfrac{1}{4}\Rightarrow-2x=-0,25-1,5\Rightarrow-2x=1,75\Rightarrow x=1,75:\left(-2\right)\Rightarrow x=...\)
\(\dfrac{3}{2}-|1.\dfrac{1}{4}+3x|=\dfrac{1}{4}\Rightarrow|1.\dfrac{1}{4}+3x|=\dfrac{3}{2}-\dfrac{1}{4}\Rightarrow|1.\dfrac{1}{4}+3x|=\dfrac{5}{4}\)
\(\Rightarrow1.\dfrac{1}{4}+3x=\pm\dfrac{5}{4}\)
\(1.\dfrac{1}{4}+3x=\dfrac{5}{4}\Rightarrow\dfrac{1}{4}+3x=\dfrac{5}{4}\Rightarrow3x=\dfrac{5}{4}-\dfrac{1}{4}\Rightarrow3x=1\Rightarrow x=3\)
\(1.\dfrac{1}{4}+3x=-\dfrac{5}{4}\Rightarrow\dfrac{1}{4}+3x=-\dfrac{5}{4}\Rightarrow3x=-\dfrac{5}{4}-\dfrac{1}{4}\Rightarrow3x=-\dfrac{3}{2}x=...\)
a: ta có: \(\left|-2x+\dfrac{3}{2}\right|=\dfrac{1}{4}\)
\(\Leftrightarrow\left[{}\begin{matrix}-2x+\dfrac{3}{2}=\dfrac{1}{4}\\-2x+\dfrac{3}{2}=-\dfrac{1}{4}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}-2x=-\dfrac{5}{4}\\-2x=-\dfrac{7}{4}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{5}{8}\\x=\dfrac{7}{8}\end{matrix}\right.\)
b: Ta có: \(\dfrac{3}{2}-\left|\dfrac{5}{4}+3x\right|=\dfrac{1}{4}\)
\(\Leftrightarrow\left|3x+\dfrac{5}{4}\right|=\dfrac{5}{4}\)
\(\Leftrightarrow\left[{}\begin{matrix}3x+\dfrac{5}{4}=\dfrac{5}{4}\\3x+\dfrac{5}{4}=-\dfrac{5}{4}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}3x=0\\3x=-\dfrac{5}{2}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-\dfrac{5}{6}\end{matrix}\right.\)
Bài 7. Tìm x,biết:
a) x-3x2=0 e) 5x(3x-1)+x(3x-1)-2(3x-1)=0
b) (x+3)2-x(x-2)=13 c) (x-4)2-36=0
d) x2-7x+12=0 g) x2-2018x-2019=0
Bài 8. Tìm x, biết
a) (2x-1)2=(x+5)2 b) x2-x+1/4
c) 4x4-101x2+25=0 d) x3-3x2+9x-91=0
Câu 3 (1,5 điểm). Tìm x, biết:
a) x + 2006 = 2021
b) 2x – 2016 = 24 x 4
c) 3(2x + 1)3 = 81
a: x=15
c: \(\Leftrightarrow2x+1=3\)
hay x=1
a) \(\Rightarrow x=2021-2006=15\)
b) \(\Rightarrow2x-2016=64\Rightarrow2x=2016+64=2080\Rightarrow x=1040\)
c) \(\Rightarrow\left(2x+1\right)^3=81:3=27\Rightarrow2x+1=3\)
\(\Rightarrow2x=3-1=2\Rightarrow x=1\)
`a) x= 15`
`b) 2x-2016=16\(\times\)4`
`⇔ 2x-2016=64`
`⇔ 2x= 2080`
`⇔ x= 1040`
`c) 3(2x+1)^3 =81`
`⇔ (2x+1)^3 =27`
`⇔ (2x+1)^3 =3^3`
`⇔ 2x+1=3`
`⇔ x= 1`
Bài 1: Lập các cặp phân số bằng nhau từ đẳng thức
a) 2 . 36 = 8 . 9
b) ( - 2 ) . ( - 18 ) = 4 . 9
Bài 2: Tìm x, y, z thuộc Z biết:
a) x/3 = - 12/ 9
b) - 4/8 = x/-10 = -7/9 = z/-24
c) - 26/13 ≤ x ≤ - 21/7
Giúp em với ạa
Bài 2 : a, x = -36/9 = -4
b, đề sai
c, <=> -2 =< x =< -3 => x = -1
Bài 1:
a: 2/8=9/36; 2/9=8/36; 8/2=36/9; 9/2=36/8
b: -2/4=9/-18; -2/9=4/-18; 4/-2=-18/9; 9/-2=-18/4
Bài 2:
a: =>x/3=-4/3
hay x=-4
Câu b đề sai rồi bạn
Tìm x biết:
a) 2x2 - 4 = 0
b) (x + 1)2 = 4
c) (2x - 1)2 - 9 = 0
d) x2 - x = 0
a: =>2x^2=4
=>x^2=2
=>\(x=\pm\sqrt{2}\)
b: =>(x+1)^2-4=0
=>(x+1+2)(x+1-2)=0
=>(x+3)(x-1)=0
=>x=1 hoặc x=-3
c: =>(2x-1)^2-3^2=0
=>(2x-1-3)(2x-1+3)=0
=>(2x-4)(2x+2)=0
=>x=2 hoặc x=-1
d: x^2-x=0
=>x(x-1)=0
=>x=0 hoặc x=1
Tìm x, y biết:
a) (x-1)(y+2)=7
b)x(y - 1) + y = 4
c) xy - 2x + y = 4
d)x^2 - 3xy + 2x - 6y = 5
`@` `\text {Ans}`
`\downarrow`
`a)`
`(x-1)(y+2)=7`
`=> (x - 1)(y + 2) \in` Ư`(7) = {7; 1; -1; -7}`
Ta có bảng sau:
`x - 1` | `7` | `1` | `-1` | `-7` |
`y + 2` | `1` | `7` | `-7` | `-1` |
`x` | `8` | `2` | `0` | `-6` |
`y` | `-1` | `5` | `-9` | `-3` |
Vậy, ta có cặp `(x; y)` thỏa mãn `{-1; 8}; {2; 5}; {-9; 0}; {-6; -3}`
`b)`
`x(y - 1) + y = 4`
`=> x(y - 1) + y - 4 = 0`
`=> x(y - 1) + (y - 1) - 3 = 0`
`=> (x + 1)(y - 1) = 3`
`=> (x + 1)(y - 1) \in` Ư`(3) = {-1; -3; 1; 3}`
Ta có bảng sau:
`x + 1` | `1` | `3` | `-1` | `-3` |
`y - 1` | `3` | `1` | `-3` | `-1` |
`x` | `0` | `2` | `-2` | `-4` |
`y` | `4` | `2` | `-2` | `0` |
Vậy, ta có cặp `(x; y)` thỏa mãn `{0; 4}; {2; 2}; {-2; -2}; {-4; 0}`
bài 2:tìm số tự nhiên x biết:
a.(2x-8).2=24
b.3.(2^x-26)=18
a) 2(2x - 8) = 24
2x - 8 = 12
2x = 20
x = 10
b)3.(2x - 26) = 18
2x - 26 = 6
2x = 32
x = 5