a) x = 3

b) x = 53

c) x = 2024

d) x = 6

`a, 504 : (16-3x)=72`

`<=> 16-3x=7`

`<=>3x=9`

`<=>x=3`

`b,272-(4x+15)=45`

`<=>4x+15=227`

`<=>4x=212`

`<=>x=53`

a: =>16-3x=504:72=7

=>3x=9

=>x=3

b: =>4x+15=272-45=227

=>4x=212

=>x=53

a) 504 : (16 - 3\(\times\)x) = 72

=> 16 - 3\(\times\)x = 7

=> 3\(\times\)x = 9

=> x = 3

d) 272 - (4\(\times\)x + 15) = 45

=> 4\(\times\)x + 15 = 227

=> 4\(\times\)x = 212

=> x = 53

Bài 10:

a: 2x-3 là bội của x+1

=>\(2x-3⋮x+1\)

=>\(2x+2-5⋮x+1\)

=>\(-5⋮x+1\)

=>\(x+1\in\left\{1;-1;5;-5\right\}\)

=>\(x\in\left\{0;-2;4;-6\right\}\)

b: x-2 là ước của 3x-2

=>\(3x-2⋮x-2\)

=>\(3x-6+4⋮x-2\)

=>\(4⋮x-2\)

=>\(x-2\inƯ\left(4\right)\)

=>\(x-2\in\left\{1;-1;2;-2;4;-4\right\}\)

=>\(x\in\left\{3;1;4;0;6;-2\right\}\)

Bài 14:

a: \(4n-5⋮2n-1\)

=>\(4n-2-3⋮2n-1\)

=>\(-3⋮2n-1\)

=>\(2n-1\inƯ\left(-3\right)\)

=>\(2n-1\in\left\{1;-1;3;-3\right\}\)

=>\(2n\in\left\{2;0;4;-2\right\}\)

=>\(n\in\left\{1;0;2;-1\right\}\)

mà n>=0

nên \(n\in\left\{1;0;2\right\}\)

b: \(n^2+3n+1⋮n+1\)

=>\(n^2+n+2n+2-1⋮n+1\)

=>\(n\left(n+1\right)+2\left(n+1\right)-1⋮n+1\)

=>\(-1⋮n+1\)

=>\(n+1\in\left\{1;-1\right\}\)

=>\(n\in\left\{0;-2\right\}\)

mà n là số tự nhiên

nên n=0

Bài 16:

a: \(\left(x+5\right)\left(y-3\right)=15\)

=>\(\left(x+5\right)\left(y-3\right)=1\cdot15=15\cdot1=\left(-1\right)\cdot\left(-15\right)=\left(-15\right)\cdot\left(-1\right)=3\cdot5=5\cdot3=\left(-3\right)\cdot\left(-5\right)=\left(-5\right)\cdot\left(-3\right)\)

=>\(\left(x+5;y-3\right)\in\left\{\left(1;15\right);\left(15;1\right);\left(-1;-15\right);\left(-15;-1\right);\left(3;5\right);\left(5;3\right);\left(-3;-5\right);\left(-5;-3\right)\right\}\)

=>\(\left(x,y\right)\in\left\{\left(-4;18\right);\left(10;4\right);\left(-6;-12\right);\left(-20;2\right);\left(-2;8\right);\left(0;6\right);\left(-8;-2\right);\left(-10;0\right)\right\}\)

mà (x,y) là cặp số tự nhiên

nên \(\left(x,y\right)\in\left\{\left(10;4\right);\left(0;6\right)\right\}\)

b: x là số tự nhiên

=>2x-1 lẻ và 2x-1>=-1

\(\left(2x-1\right)\left(y+2\right)=24\)

mà 2x-1>=-1 và 2x-1 lẻ

nên \(\left(2x-1\right)\cdot\left(y+2\right)=\left(-1\right)\cdot\left(-24\right)=1\cdot24=3\cdot8\)

=>\(\left(2x-1;y+2\right)\in\left\{\left(-1;-24\right);\left(1;24\right);\left(3;8\right)\right\}\)

=>\(\left(2x;y\right)\in\left\{\left(0;-26\right);\left(2;22\right);\left(4;6\right)\right\}\)

=>\(\left(x;y\right)\in\left\{\left(0;-26\right);\left(1;11\right);\left(2;6\right)\right\}\)

mà (x,y) là cặp số tự nhiên

nên \(\left(x,y\right)\in\left\{\left(1;11\right);\left(2;6\right)\right\}\)

c:

x,y là các số tự nhiên

=>x+3>=3 và y+2>=2

xy+2x+3y=0

=>\(xy+2x+3y+6=6\)

=>\(x\left(y+2\right)+3\left(y+2\right)=6\)

=>\(\left(x+3\right)\left(y+2\right)=6\)

mà x+3>=3 và y+2>=2

nên \(\left(x+3\right)\cdot\left(y+2\right)=3\cdot2\)

=>x=0 và y=0

d: xy+x+y=30

=>\(xy+x+y+1=31\)

=>\(x\left(y+1\right)+\left(y+1\right)=31\)

=>\(\left(x+1\right)\left(y+1\right)=31\)

\(\Leftrightarrow\left(x+1\right)\cdot\left(y+1\right)=1\cdot31=31\cdot1=\left(-1\right)\cdot\left(-31\right)=\left(-31\right)\cdot\left(-1\right)\)

=>\(\left(x+1;y+1\right)\in\left\{\left(1;31\right);\left(31;1\right);\left(-1;-31\right);\left(-31;-1\right)\right\}\)

=>\(\left(x,y\right)\in\left\{\left(0;30\right);\left(30;0\right);\left(-2;-32\right);\left(-32;-2\right)\right\}\)

mà (x,y) là cặp số tự nhiên

nên \(\left(x,y\right)\in\left\{\left(0;30\right);\left(30;0\right)\right\}\)

Tham khảo : 

\(272+\left(146-x\right)=118\)

\(146-x=118-272\)

\(146-x=-154\)

\(x=146-\left(-154\right)\)

\(\Rightarrow x=300\)

\(504:\left(16-3x\right)=72\)

\(16-3x=504:72\)

\(16-3x=7\)

\(3x=16-7\)

\(3x=9\)

\(x=9:3\)

\(\Rightarrow x=3\)

1=> 146-x=-154

=>x=300

2> =>16-3x=7

=>3x=9

=>x=3

a, 272 + ( 146 - x ) = 118

146 - x = 118 - 272

146 - x = -154

x = 146 - ( -154 )

x = 300

Vậy....

b, 504 : ( 16 - 3x ) = 72 

16 - 3x = 7

3x = 16 - 7 

3x = 9

x = 3

Vậy.....

\(a,9x-8=838\)

\(9x=838+8\)

\(9x=846\)

\(x=846:9=94\)

\(b,\left(x+30\right)-75=125\)

\(x+30=125+75\)

\(x+30=200\)

\(x=200-30=170\)

\(c,x-72:36=18\)

\(x-2=18\)

\(x=18+2=20\)

#Urushi

1.Tính nhanh nếu có thể:
a) 22 + 23 + 89 + 77
= ( 77 + 23 ) + 22 + 89
= 100 + 22 + 89
= 122 + 89
= 211
b) 35 . 15 + 15 . 65
= 15 . ( 35 + 65 )
= 15 . 100
= 1500
c) 7^2 - 36 : 3^2
=  7^2 - 36 : 9
= 7^2 - 4
= 49 - 4
= 45
d) 476 - {5 . [409 - (8 . 3 - 21)2] - 1724}
= 476 - {5 . [409 - (24 - 21)^2] - 1724}
= 476 - {5 . [409 - (3^2)] -  1724}
= 476 - {5 . [409 - 9 ] - 1724}
= 476 - {5. 400 - 1724}
= 476 - {2000 - 1724}
= 476 - 276
= 200

2. Tìm x, biết:

a) x + 37 = 50

x = 50 - 37

x = 13

b) 2x - 3 = 11

2x = 11 + 3

2x = 14

2x = 2 . 7

a,504:[16-3.x]=72

          16-3.x=504:72

          16-3.x=7

          3.x     =16-7

          3.x     =9

            \(\Rightarrow x=3\)

          b,272-[4.x+15] = 45

                   4.x+15  = 272-45

                   4.x+15  = 227

                   4.x        = 227-15

                   4.x        = 212

                      x        = 212:4

                      \(\Rightarrow x=53\)

                     c,425-x:8 =91

                              x:8 =425-91

                              x:8 =334

                              x    =334x8

                              \(\Rightarrow x=2672\)

                     d,  293-8.27+x.25=80

                         293-216 +x.25=80

                         77+x.25         =80

                               x.25         =3

                               \(\Rightarrow x=\frac{3}{25}\)

x = 3

x = 53

x = 2672

x = 3 / 25

ai thấy đúng thì ủng hộ mk nha

504:[16-3x]=72

16-3x=504:72

16-3x=7

3x=16-7

3x=9

x=9:3

x=3

Vậy x=3

272-(4x+15)=45

4x+15=272-45

4x+15=227

4x=227-15

4x=212

x=212:4

x=53

Vậy x=53

425-x:8=91

x:8=425-91

x:8=334

x=334.8

x=2672

Vậy x=2672

293-8.27+x.25=80

77+x.25=80

x.25=80-77

x.25=3

x=3:25

x=\(\frac{3}{25}\)

Vậy x=\(\frac{3}{25}\)

Bài 1: 

a: UCLN(12;52)=4

UC(12;52)={1;2;4}

504 : ( 16 - 3x ) = 72

           16 - 3x  = 504 : 72

            16 - 3x = 7

                   3x = 16 - 7

                   3x = 9

                    x = 9 : 3

                    x = 3