3a + 5 = 3.( a + 1 ) + 2 

mà  3. ( a + 1 ) \(⋮\) a + 1 

Để 3a + 5 \(⋮\) a + 1 

\(\Leftrightarrow\) 2 \(⋮\) a + 1  

\(\Rightarrow\) a + 1 \(\inƯ\left(2\right)=\left\{1;-1;2;-2\right\}\)

Ta có bảng : 

a + 1                1              - 1                  2                      - 2

a                      0               - 2                 1                        - 3 

KL                chọn           chọn             chọn                   chọn 

Vậy x \(\in\left\{0;-2;1;-3\right\}\) thì 3a + 5 \(⋮\) a + 1 

tìm số nguyên x biết  

17-2x=-21 

=> 2x = 17 - ( -21 )

=> 2x = 38

=> x  = 38 : 2

=> x  = 19

Vậy x............

|2x+1|=5 

=> 2x + 1 = 5 hoặc 2x + 1 = -5

=> 2x = 5 - 1 hoặc 2x = -5 - 1

=> 2x = 4 hoặc 2x = -6

=> x = 4: 2 hoặc x = - 6 : 2

=> x = 2 hoặc x = -3

a)125 : x = 2² - (-1)

125 : x = 4 + 1

125 : x = 5

x = 125 : 5

x = 25

-------------------------------------------------

b) 2x - 8 = -4

2x = (-4) + 8

2x = 4

x = 4 : 2 

x = 2

-----------------------------------------------------------

c) Xem lại đề.

\(125:x=2^2-\left(-1\right)\)

\(=>125:x=4+1\)

\(=>125:x=5\)

\(=>x=125:5\)

\(=>x=25\)

_____

\(2x-8=-4\)

\(=>2x=\left(-4\right)+8\)

\(=>2x=4\)

\(=>x=4:2\)

\(=>x=2\)

_______

\(6^{2x+5}=216\)

\(=>6^{2x+5}=6^3\)

\(=>2x+5=3\)

\(=>2x=3-5\)

\(=>2x=-2\)

\(=>x=\left(-2\right):2\)

\(=>x=-1\)

\(#NqHahh\)

125:x=2² - (-1)

125:x=4+1

125:x=5

X=125:5

X=25

2x -8 = -4

2x=-4+8

2x=4

X=4:2

X=2

6²(x+5)  = 216

36(x+5) = 216

X+5 = 216:36

X+5=6

X=6-5

X=1

a) \(\frac{-x}{2}+\frac{2x}{3}+x+\frac{1}{4}+2x+\frac{1}{6}=\frac{3}{8}.\)

\(\frac{-x}{2}+\frac{2x}{3}+3x+\frac{5}{12}=\frac{3}{8}\)

\(x.\left(-\frac{1}{2}+\frac{2}{3}+3\right)+\frac{5}{12}=\frac{3}{8}\)

\(x\cdot\frac{19}{6}=-\frac{1}{24}\)

x = -1/76

b) \(\frac{3}{2x+1}+\frac{10}{4x+2}-\frac{6}{6x+3}=\frac{12}{26}\)

\(\frac{3}{2x+1}+\frac{2.5}{2.\left(2x+1\right)}-\frac{2.3}{3.\left(2x+1\right)}=\frac{6}{13}\)

\(\frac{3}{2x+1}+\frac{5}{2x+1}-\frac{2}{2x+1}=\frac{6}{13}\)

\(\frac{3+5-2}{2x+1}=\frac{6}{13}\)

\(\frac{6}{2x+1}=\frac{6}{13}\)

=> 2x + 1 = 13

2x = 12

x = 6