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`-2/5 : x=1/2`
`=> x= -2/5 : 1/2`
`=> x= -2/5 xx 2`
`=>x= -4/5`
__
`7/6 : x = 7/4`
`=>x= 7/6 : 7/4`
`=>x=7/6 xx 4/7`
`=>x= 28/42`
`=>x=2/3`
![](https://rs.olm.vn/images/avt/0.png?1311)
Câu 2:
a: \(\Leftrightarrow x+2\in\left\{3;9\right\}\)
hay \(x\in\left\{1;7\right\}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Trl:
\(\left(3x-2^4\right).7^{10}=2.7^{10}\)
\(\Rightarrow\left(3x-16\right)=2.7^{10}:7^{10}\)
\(\Rightarrow\left(3x-16\right)=2.1\)
\(\Rightarrow\left(3x-16\right)=2\)
\(\Rightarrow3x=16+2\)
\(\Rightarrow3x=18\)
\(\Rightarrow x=18:3\)
\(\Rightarrow x=6\)
Hc tốt
\(\left(3x-2^4\right)\times7^{10}=2\times7^{10}\)
\(3x-2^4=2\times7^{10}:7^{10}\)
\(3x-2^4=2\times1\)
\(3x-16=2\)
\(3x=18\)
\(x=6\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
(x2 + 7).(x2 - 49) < 0
+) x2 + 7 < 0 (vô lí, loại); x2 - 49 > 0
+) x2 + 7 > 0 (luôn đúng); x2 - 49 < 0
=> x2 - 49 < 0
=> x2 < 49
=> x2 < 72 = (-7)2
=> x < 7 hoặc x < -7
Vạy x < 7.
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( ( x . 32 ) - 17 ) . 2 = 42
( ( x . 32 ) - 17 ) = 42 : 2
( ( x . 32 ) - 17 ) = 21
x . 32 = 21 + 17
x . 32 = 38
x = 38 : 32
x = 19/16
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,-2.\left(x+7\right)+3.\left(x-2\right)=-2\)
\(-2x-14+3x-6=-2\)
\(x-20=-2\)
\(x=-2+20\)
\(x=18\)
\(b,-7-2x=-37-\left(-26\right)\)
\(-7-2x=-11\)
\(-2x=-11+7\)
\(-2x=-4\)
\(x=2\)
\(c,\left(3x+9\right).\left(11-x\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}3x+9=0\\11-x=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=-3\\x=11\end{cases}}}\)
\(\orbr{\begin{cases}3x+9=0\\11-x=0\end{cases}}\Rightarrow\orbr{\begin{cases}3x=-9\\x=11\end{cases}}\Rightarrow\orbr{\begin{cases}x=-3\\x=11\end{cases}}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
2/7.x+20%.x=7/4
=> 2/7.x+1/5.x = 7/4
=> x. ( 2/7+1/5)=7/4
=> x . 17/35 = 7/4
=> x = 7/4 : 17/35
=> x = 1/340
X = \(\frac{1}{340}\)
TÍCH MIK NHA Dương Anh Kiệt
HÃY TÍCH CHO MIK 1 TÍCH THÔI CŨNG ĐƯỢC
![](https://rs.olm.vn/images/avt/0.png?1311)
2. ( x-2 ) + 7 = x - 25
2x - 4 +7 -x + 25 = 0
x + 28 = 0
x = 0 - 28
x = -28
Vậy x = -28
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có : (x + 3) + (x + 5) + (x + 7) + ..... + (x + 21) = 335
=> x + x + x + x + (3 + 5 + 7 + ..... + 21) = 335
=> 10x + 120 = 335
=> 10x = 335 - 120
=> 10x = 215
=> x = 21,5
ta có : (x + 3) + (x + 5) + (x + 7) + ..... + (x + 21) = 335
<=> x + x + x + x + (3 + 5 + 7 + ..... + 21) = 335
<=> 10x + 120 = 335
=> 10x = 335 - 120
=> 10x = 215
vậy x = 21,5
(x+2)7=(x+2)6
(x+2).(x+2)6=(x+2)6
(x+2).(x+2)6-(x+2)6=0
(x+2)6.(x+2-1) = 0
(x+2)6=0 hoặc x+1=0
x=-2 hoặc x=-1
Vậy x thuộc {-1; 0}