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Lời giải:
a. $8-3x=(-7)^2:(-7)=(-7)$
$\Rightarrow 3x=8-(-7)=15$
$\Rightarrow x=15:3=5$
b.
$18\vdots x, 24\vdots x$ nên $x\in ƯC(18,24)$
$\Rightarrow ƯCLN(18,24)\vdots x$
Hay $6\vdots x$
$\Rightarrow x\in\left\{\pm 1; \pm 2; \pm 3; \pm 6\right\}$
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a: \(\dfrac{-4}{8}=\dfrac{x}{-10}=\dfrac{-7}{y}=\dfrac{z}{-24}\)
=>\(\dfrac{x}{-10}=\dfrac{-7}{y}=\dfrac{z}{-24}=\dfrac{-1}{2}\)
=>\(\left\{{}\begin{matrix}x=\left(-10\right)\cdot\dfrac{\left(-1\right)}{2}=5\\y=\dfrac{-7\cdot2}{-1}=14\\z=\dfrac{-24\cdot\left(-1\right)}{2}=\dfrac{24}{2}=12\end{matrix}\right.\)
b: \(\dfrac{-3}{6}=\dfrac{x}{-2}=\dfrac{-18}{y}=\dfrac{-z}{24}\)
=>\(\dfrac{x}{-2}=\dfrac{-18}{y}=\dfrac{z}{-24}=\dfrac{-1}{2}\)
=>\(\dfrac{x}{2}=\dfrac{18}{y}=\dfrac{z}{24}=\dfrac{1}{2}\)
=>\(x=2\cdot\dfrac{1}{2}=1;y=18\cdot\dfrac{2}{1}=36;z=\dfrac{24}{2}=12\)
![](https://rs.olm.vn/images/avt/0.png?1311)
18-25=2(7-x)-(25+24)
-7=2(7-x)-49
2(7-x)=(-7)+49
2(7-x)=42
7-x=42:2
7-x=21
x=21+7
x=28
Vậy x=28
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a ) x - ( - 18 ) = -24
x + 18 = -24
x = -24 - 18
x = -6
b ) -x - 17 + 8 = 33 - 19
-x - 17 + 8 = 14
-x - 17 = 14 - 8
-x - 17 = 6
-x = -( 6 + 17 )
-x = - 23
c ) 15 - ( -4 + 7 ) = x - 14
15 + 4 + 7 = x - 14
27 = x - 14
x - 14 = 27
x = 27 + 14
x = 41
d ) 9 - 25 = ( 7 - x ) - ( 25 + 7 )
( 7 - x ) - 32 = -16
7 - x = -16 + 32
-7 - x = -16
x = -7 - ( - 16)
x = -7 + 16
x = 9
![](https://rs.olm.vn/images/avt/0.png?1311)
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-12 + 3(-x + 7 ) = -18
3(-x + 7 ) = (-18 ) - (-12)
3(-x + 7 ) = -6
-x + 7 = (-6) : 3
- x + 7 = 2
-x = 2-7
-x = -5
vậy x = 5
24 : ( 3x - 2 ) = -3
3x - 2 = 24 : (-3)
3x - 2 = -8
3x = -8 + 2
3x = -6
x = (-6) : 3
x = -2
vậy x = -2
-45 : 5(-3 - 2x ) = 3
5( -3 - 2x ) = (-45) : 3
5( -3 - 2x ) = -15
-3 - 2x = (-15) : 5
-3 - 2x = (-3)
2x = (-3) : (3)
2x = 0
x = 2 : 0
x = 0
vậy x = 0
![](https://rs.olm.vn/images/avt/0.png?1311)
a, x = {45;60}
b, x = {35;42;49;56;63;70}
c, x = {36;54;72;90}
d, x = {36;48;60;72;84;96}
e, x = {25;30;35;40;45;50;55;60}
f, x = {27;30;33;36;39;42;45;48;51;54;57}
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a) 4x- 15 = -75 - x
=> 4x + x = -75 + 15
=> 5x = -60
=> x = -60 : 5
=> x = -12
b) 3(x - 7) = 21
=> x - 7 = 21 : 3
=> x - 7 = 7
=> x = 7 + 7
=> x = 14
c) \(-\frac{3}{6}=\frac{x}{-2}=\frac{-18}{y}=\frac{-z}{24}\)
Ta có: +) \(-\frac{3}{6}=\frac{x}{-2}\) => \(\frac{1}{-2}=\frac{x}{-2}\) => x = 1
+) \(\frac{-3}{6}=\frac{-18}{y}\) => \(\frac{-18}{36}=\frac{-18}{y}\) => y = 36
+) \(-\frac{3}{6}=\frac{-z}{24}\) = > \(\frac{-12}{24}=\frac{-z}{24}\) => -z = -12 => z = 12
d) \(-\frac{8}{3}+\frac{-1}{4}< x< \frac{-2}{7}+\frac{-5}{7}\)
=> \(\frac{-32}{12}-\frac{3}{12}< x< \frac{-2-5}{7}\)
=> \(\frac{-35}{12}< x< -1\)
=> x = -2 (x \(\in\)Z)
a) 4x - 15 = -75 - x
4x + x = -75 + 15
5x = -60
=> x = -60 : 5 = -12
=>31x=354+18=372
=>x=372:31=12
Vậy x=12.
Hok tốt!!
24.x-18+7.x=354
\(\Rightarrow\)x.(24+7)=354+18=372
\(\Rightarrow\)x.31=372
\(\Rightarrow\)x =12