k,x (3-x) = 0 m, (x+2).(4x-8) = 0 p,21x - 17 - 15x = 25
q,123 - 5 (x+4) = 38 r, 1 - (3x -15) : 3 = 0 s,23 + 17 (x+1)= 108
Giúp với ạ T^T
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\(6.\left(x-39\right)=18\\ \left(x-39\right)=18:6\\ \left(x-39\right)=3\\ x=3+39\\ x=42.\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
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(x - 5) - (2x + 7) = -8
x - 5 - 2x - 7 = - 8
-x - 5 - 7 = -8
-x - 12 = -8
-x = -8 + 12
-x = 4
x = -4.
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` 25 xx (y- 40) = 0`
`y - 40 = 25 : 0`
`y - 40 = 0`
`y = 0 + 40`
`y = 40`
(25:0 = không xác định nhé lêmaichale
25x (y-40) = 0
y- 40 = 0 : 25
y - 40 = 0
Y= 40 + 0
Y = 40
![](https://rs.olm.vn/images/avt/0.png?1311)
`2 xx y - 15 = 17`
`2 xx y = 17 + 15`
`2 xx y= 32`
`y =32 : 2`
`y = 16`
______________________
`3 xx y + 4 = 19`
`3 xx y = 19 -4`
`3 xx y =15`
`y =15 : 3`
`y =5`
_______________________
`55 - 2 xx y = 13`
`2xx y = 55 - 13`
`2xxy =42`
`y = 42:2`
`y= 21`
`2 xx y - 15 = 17`
`2 xx y = 17 + 15`
`2 xx y= 32`
`y =32 : 2`
`y = 16`
`3 xx y + 4 = 19`
`3 xx y = 19 -4`
`3 xx y =15`
`y =15 : 3`
`y =5`
`55 - 2 xx y = 13`
`2xx y = 55 - 13`
`2xxy =42`
`y = 42:2`
`y= 21`
![](https://rs.olm.vn/images/avt/0.png?1311)
Gọi số học sinh trường đó là : `x` ( `350 < x < 400)`
Theo đề ta có :
`x ∈` \(BCNN\left(4,5,6\right)\)
`4 = 2^2`
`5 = 1.5`
`6 = 2.3`
`BCNNN ( 4,5,6) = 2^2 . 3 .5 = 60`
`=> x ∈ B (60) = { 0,60,120,180,240,300,360,420.....}`
Mà `350 < x < 400`
`=> x = 360`
Vậy số hoc sinh khối `6` là : `360` học sinh
x ( 3 - x ) = 0
x = 0 hoặc 3 - x = 0
x = 3 - 0
x = 3
Vậy x = 0; x = 3
( x + 2 ) . ( 4x - 8 ) = 0
x + 2 = 0
x = 0 - 2
x = -2
4x - 8 = 0
4x = 8
x = 2
Vậy x = -2; x = 2
21x - 17 - 15x = 25
21x - 15x - 17 = 25
6x - 17 = 25
6x = 25 + 17
6x = 42
x = 7
123 - 5 ( x + 4 ) = 38
5 ( x + 4 ) = 123 - 38
5 ( x + 4 ) = 85
( x + 4 ) = 17
x = 13
1 - ( 3x-15) : 3 = 0
( 3x - 15 ) : 3 = 1 - 0
( 3x - 15 ) : 3 = 1
( 3x - 15 ) = 3
3x = 18
x= 6
23 + 17 ( x+1 ) = 108
17 ( x+1 ) = 85
( x + 1 ) = 5
x = 4
`x.(3-x) = 0`
`=>` \(\left[{}\begin{matrix}x=0\\3-x=0\end{matrix}\right.=>\left[{}\begin{matrix}x=0\\x=3\end{matrix}\right.\)
`(x +2).(4x-8) = 0`
`=>` \(\left[{}\begin{matrix}x+2=0\\4x-8=0\end{matrix}\right.=>\left[{}\begin{matrix}x=-2\\4x=8\end{matrix}\right.=>\left[{}\begin{matrix}x=-2\\x=2\end{matrix}\right.\)
`21x - 17 - 15x = 25`
`(21x-15x)-17=25`
`6x-17=25`
`6x = 42`
`x =42:6`
`x=7`
`123 - 5.(x+4)=38`
`5.(x+4) = 123-38`
`5.(x+4) =85`
`x+4=85:5`
`x+4=17`
`x=17-4`
`x=13`
`1-(3x-15):3=0`
`3x-15:3=1`
`3x - 5 = 1`
`3x = 6`
`x=6:3`
`x=2`
`23+17.(x+1) =108`
`17.(x+1) = 108 - 23`
`17.(x+1) =85`
`x+1=85:17`
`x+1=5`
`x=5-1`
`x=4`