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1)\(x=\left(\dfrac{1}{5}+\dfrac{2}{3}\right):\dfrac{4}{7}=\left(\dfrac{3}{15}+\dfrac{10}{15}\right):\dfrac{4}{7}=\dfrac{13}{15}:\dfrac{4}{7}=\dfrac{91}{60}\)
2)\(x=\left(-\dfrac{3}{10}-\dfrac{3}{4}\right):\dfrac{1}{2}=\left(-\dfrac{6}{20}-\dfrac{15}{20}\right):\dfrac{1}{2}=-\dfrac{21}{20}:\dfrac{1}{2}=-\dfrac{21}{10}\)
3)\(x=-\dfrac{24}{36}-\dfrac{7}{15}=-\dfrac{2}{3}-\dfrac{7}{15}=\dfrac{-10}{15}-\dfrac{7}{15}=-\dfrac{17}{15}\)
1) \(\dfrac{4}{7}x=\dfrac{1}{5}+\dfrac{2}{3}\)
\(\dfrac{4}{7}x=\dfrac{13}{15}\)
\(x=\dfrac{91}{60}\)
2) \(\dfrac{1}{2}x=-\dfrac{3}{10}-\dfrac{3}{4}\)
\(\dfrac{1}{2}x=-\dfrac{21}{20}\)
\(x=-\dfrac{21}{10}\)
3) \(x=-\dfrac{24}{36}-\dfrac{7}{15}\)
\(x=\dfrac{-2}{3}+\dfrac{7}{15}\)
\(x=-\dfrac{17}{15}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
1: x=7+5=12
2: =>-29-x=-10
=>x+29=10
=>x=-19
3: =>x+7=-18
=>x=-25
4: =>x+19-11=0
=>x+8=0
=>x=-8
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(x-7).(2x-8)=0
suy ra :(x-7)=0 suy ra x=7
2x-8=0 suy ra x=4
Câu b:
( x-40) .15 =15.3
(x-40) .15=45
(x-40) = 45:15
x-40 = 3
x=43
Bài 1: Tìm x biết:
a ) (x-7).(2x-8)=0
=>x-7=0 hoặc 2x-8=0
=>x=7 hoặc x=4
b) (x-40).15=15.3
=>(x-40).15=45
=>x-40=45:15
=>x-40=3
=>x=3+40
=>x=43
![](https://rs.olm.vn/images/avt/0.png?1311)
a)x-63:9=18
x-63 =18.9
x-63 =162
x =162+63
x =225
b)3(29-x)+52=103
3(29-x) =103-52
3(29-x) =51
29-x =51:3
29-x =17
x =12
c)|x-1|=4
=>x-1=4 hoặc x-1= -4
=>x=5 hoặc x= -3
d)(-7)-x= -21
x=(-7)-(-21)
x=14
a) x-63;9=18
x-7=18
x=18+7=25
b)3(29-x)=103-52
87-3x=51
-3x=51-87=-36
x=12
c)
* x-1 =4
x=5
* x-1=-4
x=-3
d)(-7)-x=-21
-x=-21+7=14
x=14
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(x+5=20-\left(12-7\right)\)
\(\Rightarrow x+5=20-5\)
\(\Rightarrow x+5=15\)
\(\Rightarrow x=15-5\)
\(\Rightarrow x=10\)
b) \(15-\left(3+2x\right)=2^2\)
\(\Rightarrow3+2x=15-4\)
\(\Rightarrow3+2x=11\)
\(\Rightarrow2x=11-3\)
\(\Rightarrow2x=8\)
\(\Rightarrow x=\dfrac{8}{2}\)
\(\Rightarrow x=4\)
c) \(-11-\left(19-x\right)=50\)
\(\Rightarrow19-x=-11-50\)
\(\Rightarrow19-x=-61\)
\(\Rightarrow x=61+19\)
\(\Rightarrow x=80\)
d) \(159-\left(25-x\right)=43\)
\(\Rightarrow25-x=159-43\)
\(\Rightarrow25-x=116\)
\(\Rightarrow x=25-116\)
\(\Rightarrow x=-91\)
e) \(\left(79-x\right)-43=-\left(17-52\right)\)
\(\Rightarrow\left(79-x\right)-43=52-17\)
\(\Rightarrow79-x-43=35\)
\(\Rightarrow36-x=35\)
\(\Rightarrow x=1\)
f) \(\left(7+x\right)-\left(21-13\right)=32\)
\(\Rightarrow7+x-8=32\)
\(\Rightarrow x-1=32\)
\(\Rightarrow x=32+1\)
\(\Rightarrow x=33\)
g) \(-x+20=-15+8+13\)
\(\Rightarrow-x+20=6\)
\(\Rightarrow x=20-6\)
\(\Rightarrow x=14\)
h) \(-\left(-x+13-142\right)+18=55\)
\(\Rightarrow x-13+142+18=55\)
\(\Rightarrow x+147=55\)
\(\Rightarrow x=55-147\)
\(\Rightarrow x=-92\)
![](https://rs.olm.vn/images/avt/0.png?1311)
17x + 3. ( -16x – 37) = 2x + 43 - 4x
<=>17x-48x-111=-2x+43
<=>-29x=154
<=> \(x=-\frac{154}{29}\)
-3. (2x + 5) -16 < -4. (3 – 2x)
\(\Leftrightarrow-6x-31< -12+8x.\)
\(\Leftrightarrow-14x< 19\Rightarrow x< -\frac{19}{14}\)
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`1, -2/9 xx 15/17 + (-2/9) xx 2/17`
`= -2/9 xx (15/17 + 2/17)`
`= -2/9 xx 17/17`
`=-2/9xx1`
`=-2/9`
__
`-5/3 xx 6/5 + (-7/9) xx 3/10`
`= -30/15 + (-21/90)`
`= -2 + (-7/30)`
`=-60/30 +(-7/30)`
`=-67/30`
__
`15/20 xx 7/5 + (-9/7) xx (-6/4)`
`=3/4 xx7/5 + (-9/7) xx(-6/4)`
`= 21/20 + 54/28`
`= 21/20 + 27/14`
`=417/140`
__
`-25/13 xx 5/19 + (-25/13) xx 14/19`
`=-25/13 xx (5/19 +14/19)`
`=-25/13 xx 19/19`
`= -25/13 xx 1`
`=-25/13`
__
`-7/13 xx 13/5 + (-9/7) xx 5/3`
`=-7/5 +(-15/7)`
`=-124/35`
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a) 5 6 + 1 6 ≤ x ≤ 13 4 + 14 8 ⇔ 1 ≤ x ≤ 5 ⇔ x ∈ 1 ; 2 ; 3 ; 4 ; 5
b) − 5 6 + 8 3 + 29 − 6 ≤ x ≤ − 1 2 + 2 + 5 2 ⇔ − 3 ≤ x ≤ 4 ⇔ x ∈ − 3 ; − 2 ; − 1 ; 0 ; 1 ; 2 ; 3 ; 4
c) 79 15 + 7 5 + − 8 3 ≤ x ≤ 10 3 + 15 4 + 23 12 ⇔ 4 ≤ x ≤ 9 ⇔ x ∈ 4 ; 5 ; 6 ; 7 ; 8 ; 9
1) X = 49 2) 0
x=84 ;0