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38.x-x.12-x.16=40
<=> x(38-12-16)=40
<=> x.10=40
<=>x =4
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a) Ta có : \(x⋮12\Rightarrow x\in B\left(12\right)=\left\{12;24;36;48;...\right\}\) (sửa \(x\in12\rightarrow x⋮12\))
mà \(0< x< 40\)
\(\Rightarrow x\in\left\{12;24;36\right\}\)
b) \(16⋮x\Rightarrow x\in U\left(16\right)=\left\{1;2;4;8;16\right\}\left(x\inℕ\right)\) (sửa \(16\in x\rightarrow16⋮x\))
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{12}{16}=-\frac{x}{4}=\frac{21}{y}=\frac{z}{-80}\)
Ta có : \(\frac{12}{16}=-\frac{x}{4}\Rightarrow16.-x=12.4\Rightarrow16.-x=48\)
\(\Rightarrow-x=3\Rightarrow x=-3\)
\(\frac{12}{16}=\frac{21}{y}\Rightarrow12.y=16.21\Rightarrow12.y=336\)
\(\Rightarrow y=28\)
\(\frac{12}{16}=\frac{z}{-80}\Rightarrow16.z=12.-80\Rightarrow16.z=-960\)
\(\Rightarrow z=60\)
Vậy x = - 3 ; y = 28 ; z = 60
Ta có:
\(\frac{12}{16}=\frac{-x}{4}=\frac{21}{y}=\frac{z}{-80}\)
\(\Leftrightarrow\frac{12}{16}=\frac{-x}{4}=\frac{21}{y}=\frac{-z}{80}\) (Chuyển mẫu âm thành dương)
\(\frac{-x}{4}=\frac{12}{16}=\frac{12:\left(-4\right)}{16:\left(-6\right)}=\frac{-3}{-4}=\frac{3}{4}\Rightarrow x=-3\) (Ta chuyển mẫu âm thành dương)
\(\frac{21}{y}=\frac{3}{4}=\frac{3.7}{4.7}=\frac{21}{28}\Rightarrow y=28\)
\(\frac{-z}{80}=\frac{21}{28}\) ( Vì 80 : 28 không hết) \(\Rightarrow z=\varnothing\)
\(\Rightarrow\hept{\begin{cases}-3\\28\\\varnothing\end{cases}}\)
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+) 187 x ( 38 + 62 ) - 87 x ( 62 + 38 )
= ( 62 + 38 ) x ( 187 - 87 )
= 100 x 100
= 10000
p/s : làm từng phần đợi mk chút ^^
25 x { 32 : [ 12 - 4 + 4 x ( 16 : 8 ) ] }
= 25 x { 32 : [ 8 + 4 x 2 ] }
= 25 x { 32 : 16 }
= 25 x 2
= 50
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`12^4 .x-3.x=145-225:51`
`=>20736x-3x=145-75/17`
`=>20733x=2390/17`
`=>x=2390/17:20733`
`=>x=2390/352461`
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có: \(\hept{\begin{cases}|x-40|\ge0;\forall x,y\\|x-y+10|\ge0;\forall x,y\end{cases}}\)
\(\Rightarrow|x-40|+|x-y+10|\ge0;\forall x,y\)
Do đó: \(|x-40|+|x-y+10|=0\)
\(\Leftrightarrow\hept{\begin{cases}|x-40|=0\\|x-y+10|=0\end{cases}}\Leftrightarrow\hept{\begin{cases}x=40\\y=50\end{cases}}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
38 - x.12 - x.16 = 40
38 - x.(12+16) = 40
38 - 28.x = 40
28.x = 40 - 38
28.x = 2
x= 2/28
x=1/14