8 ⋮ \(x\);  12 ⋮  \(x\);  24 ⋮ \(x\) ⇒ 8; 12; 24 ⋮ \(x\) ⇒ \(x\) \(\in\) ƯC(8;12;24)

8 = 2³; 12 = 2².3; 24 = 2².3

ƯCLN(8; 12; 24) =  2² = 4

\(x\) \(\in\) {-4;  -2; -1; 1; 2; 4}

a) 4
b) 6
c) 2

b, 24 ⋮ \(x\); 30 ⋮ \(x\) ⇒ \(x\) \(\in\) ƯC(24; 30) 

24 = 2³.3; 30 = 2.3.5 ⇒ ƯCLN(24; 30) = 2.3 = 6

\(x\) \(\in\) Ư(6) = {-6; -3; -2; -1; 1; 2; 3; 6}

Tính giá trị của biểu thức:

a)  324 – 20 + 61 = 356

b) 21 x 3 : 9  = 7

c)  201 + 39 : 3  = 214

d) 123 x (42 - 38) = 528

a,91-5(5+x)=61

=>25+5x=91-61=30

=>5x=30-25=5

=>x=1

b,\([\left(x+34\right)-50]\)x2=56

=>(x+34)-50=56:2=28

=>x+34=28+50=78

=>x=78-34=44.

c,1045-\([2015-\left(3x-24\right)]\)=5

=>2015-(3x-24)=1045-5=1040

=>3x-24=2015-1040=975

=>3x=975+24=999

=>x=999:3=333

d,\([195-\left(3x-27\right)]\)x39=4212

=>195-(3x-27)=4212:39=108

=>3x-27=195-108=87

=>3x=87+27=117

=>x=39

e,30-3(x-2)=18

=>30-3x+6=18

=>30-3x=18-6=12

=>3x=30-12=18

=>x=18:3=6

a) \(...\Rightarrow5\left(5+x\right)=91-61=30\)

\(\Rightarrow\left(5+x\right)=30:5=6\Rightarrow x=6-5=1\)

b) \(...\Rightarrow\left(x+34\right)-50=56:2=28\)

\(\Rightarrow\left(x+34\right)=28+50=78\Rightarrow x=78-34=44\)

c) \(...\Rightarrow2015-\left(3x-24\right)=1045-5=1040\)

\(\Rightarrow\left(3x-24\right)=2015-1040=975\)

\(\Rightarrow3x=975+24=999\Rightarrow x=999:3=333\)

d) \(...\Rightarrow195-\left(3x-27\right)=4212:39=108\)

\(\Rightarrow\left(3x-27\right)=195-108=87\)

\(\Rightarrow3x=87+27=114\Rightarrow x=114:3=38\)

e) \(...\Rightarrow3\left(x-2\right)=30-18=12\Rightarrow x-2=12:3=4\)

\(\Rightarrow x=4+2=6\)

a) 320 x 63 - 16 x 20 + 32 x 370

= 320 x 63 - 320 x + 320 x 37

= 320 x ( 63 - 1 + 37 )

= 320 x 99 

= 320 x ( 100 - 1 )

= 320 x 100 - 320

= 32000 - 320 = 31 680

b) 35 x 61 + 215 x 5 + 35 x 39 + 57 x 25

= 5 x 427 + 5 x 215 + 5 x 273 + 5 x 285

= 5 x ( 427 + 215 + 273 + 285 ) 

= 5 x 1200 = 6000

c) 34 x 24 - 94 x 6 + 83 x 48 - 47 x 88

= 204 x 4 - 4 x 141 + 996 x 4 - 1034 x 4

= 4 x ( 204 - 141 + 996 - 1034 )

= 4 x 25 = 100

-5 - (24 - x ) = 12 + (42-65)

\(\Leftrightarrow\) -5-24-x = 12+42-65

\(\Leftrightarrow\) x - 29 = -11

\(\Leftrightarrow\) x = -11+29

\(\Leftrightarrow\) x = 18

a,-5 - (24 - x ) = 12+(42-65 )

-> -5 - (24-x) = 12+ ( -23)

-> -5 - (24-x) = -11

-> - (24-x) = -11 - 5

->- (24-x) = -16

->24-x = 16

-> x = 18

Vậy x = 18

-5 - (24 - x ) = 12+(42-65 )

-> -5 - (24-x) = 12+ ( -23)

-> -5 - (24-x) = -11

-> - (24-x) = -11 - 5

->- (24-x) = -16

->24-x = 16

-> x = 18

tui cũng ko làm đc giống bà.Khi nào có câu trả lời nhớ nói tui nha

ok babe , s bà chặn fb tui z nhi

a) 

+ Ta thấy 

72/49 > 1

72/54 <1

vậy 72/49 > 47/54

b) 34/39 và 61/63

+ Ta thấy 

61/39 > 1

61/63 <1

vậy 34/39 > 61/63

c) 

+ ta thấy 

42/39 > 1 

42/49 <1

vậy 37/39 > 42/49

khó hiểu 1 chút nhưng đúng đó 

nha 

39 x 25 + 78 x 16 + 39 + 39 x 42

= 39 x 25 + 2 x16  + 39 + 39 x 42

= 39 x (25 + 2 + 1 + 42)

= 39 x 70

= 2730

a) `123 - 27 + 27 + 13 - 123`

`= (123 - 123) + (27 - 27) + 13`

`= 0 + 0 + 13`

`= 13`

`---`

b) `175 + 25 + 13 + 15 - 175 - 25`

`= (175-175)+(25-25)+25+13`

`=0+0+25+13`

`=28`

`---`

c) \(53\times39+47\times39+53\times21+47\times21\)

\(=\text{[}\left(53+47\right)\times39]+\left[\left(53+47\right)\times21\right]\)

\(=\left(100\times39\right)+\left(100\times21\right)\)

\(=3900+2100\)

`=6000`

`---`

d) \(49\times35+49\times16-49\times61\)

`=` \(49\times\left(35+16-61\right)\)

`=` \(49\times\left(-10\right)\)

`=-490`