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Câu 1
a) \(48=2^4.3\)
\(60=2^2.3.5\)
\(72=2^3.3^2\)
\(ƯCLN\left(48;60;72\right)=2^2.3=12\)
\(ƯC\left(48;60;72\right)=Ư\left(12\right)=\left\{1;2;3;4;6;12\right\}\)
b) \(42=2.3.7\)
\(55=5.11\)
\(91=7.13\)
\(ƯCLN\left(42;55;91\right)=1\)
\(ƯC\left(42;55;91\right)=\left\{1\right\}\)
c) \(48=2^4.3\)
\(72=2^3.3^2\)
\(ƯCLN\left(48;72\right)=2^3.3=24\)
\(ƯC\left(48;72\right)=Ư\left(24\right)=\left\{1;2;3;4;6;8;12;24\right\}\)
Câu 2:
120 ⋮ \(x\); 168 ⋮ \(x\); 216 ⋮ \(x\);
\(x\) \(\in\) ƯC(120; 168; 216)
120 = 23.3.5; 168 = 23.3.7; 216 = 23.33
ƯClN(120; 168; 216) = 23.3 = 24
\(x\) \(\in\) Ư(24) = {1; 2; 3; 4; 6; 8; 12; 24}
Vì \(x\) > 20 nên \(x\) = 24
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A = 78 x 31 + 78 x 24 + 78 x 17 + 22 x 72
A = 78 x ( 31 + 24 + 17 ) + 22 x 72
A = 78 x 72 + 22 x 72
A = 72 x ( 78 + 22 )
A = 72 x 100
A = 7200
C = 53 x 39 + 47 x 39 - 53 x 21 - 47 x 21
C = 39 x ( 53 + 47 ) - 21 x ( 53 - 47 )
C = 39 x 100 - 21 x 6
C = 3900 - 126
C = 3774
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39 + (31 - x) = 70
31 - x = 70 - 39
31 - x = 31
x = 31 - 31
x = 0
39 + ( 31 - x ) = 70
31 - x = 70 - 39
31 - x = 31
x = 31 - 31
x = 0 .
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a) 39 + ( 31 - x ) = 70
31 - x = 39 + 70
31 - x = 109
=> x = 31 - 109
=> x = -78
39 + ( 31 - x ) = 70
31 - x = 70 - 39
31 - x = 31
x = 31 - 31
x = 0
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\(\left(-x+31\right)-39=69+11\Leftrightarrow-x+31-39=80\)
\(\Leftrightarrow\) \(-x=80+39-31=88\) \(\Leftrightarrow\) \(x=-88\) vậy \(x=-88\)
\(\left(-x+31\right)-39=69+11\)
\(\Leftrightarrow\left(-x+31\right)-39=80\)
\(\Leftrightarrow-x+31=80+39\)
\(\Leftrightarrow-x+31=119\)
\(\Leftrightarrow-x=119-31\)
\(\Leftrightarrow-x=88\Rightarrow x=-88\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\Leftrightarrow\) \(-x=-58+39-31=-50\) \(\Leftrightarrow\) \(x=50\) vậy \(x=50\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(x-68:69-\left(48-24.2:6-3\right)=0\)
\(x-\frac{68}{69}-\left(48-8-3\right)=0\)
\(x-\frac{68}{69}-37=0\)
\(x-\frac{68}{69}=37\)
\(x=\frac{2621}{69}\)
x - 68 : 69 - (48 - 24 * 2 : 6 - 3) = 0
x - 68 : 19 - 48 + 24 x 2 : 6 + 3 = 0
x - 68 : 19 - 48 + 24 x 2: 6 = 0 + 3
x - 68 : 19 - 48 + 24 x 2: 6 = 3
x - 68 : 19 - 48 + 24 x 2 = 3 x 6
x - 68 : 19 - 48 + 24 x 2 = 18
x - 68 : 19 - 48 + 24 = 18 : 2
x - 68 : 19 - 48 + 24 = 9
x - 68 : 19 - 48 = 9 - 24
x - 68 : 19 - 48 = -15
x - 68 : 19 = ( - 15 ) + 48
x - 68 : 19 = 33
x - 68 = 33 x 19
x - 68 = 627
x = 627 + 68
x = 695
k cho mik nha làm ơn đi mn
39 x31+ 39x68 +39
=39x(31+68+1)
=39x100
=3900
39x3x(31+68)
=117 x (31+68)
117 x 99
= 11583