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\(1\)) \(70:\frac{4x+720}{x}=\frac{1}{2}\)
\(\Leftrightarrow\frac{4x+720}{x}=70:\frac{1}{2}\)
\(\Leftrightarrow\frac{4x+720}{x}=140\)
\(\Leftrightarrow\left(4x+720\right):x=140\)
\(\Leftrightarrow4x+720=140.x\)
\(\Leftrightarrow4x-140x=-720\)
\(\Leftrightarrow x.\left(-136\right)=-720\)
\(\Leftrightarrow x=-720:\left(-136\right)\)
\(\Leftrightarrow x=\frac{90}{17}\)
\(2\)) Mình đang nghĩ
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(2\left(x-5\right)-3\left(x+7\right)=14\)
\(\Leftrightarrow2x-10-3x-21=14\)
\(\Leftrightarrow-x-31=14\)
\(\Leftrightarrow-x=45\Leftrightarrow x=-45\)
b) \(5\left(x-6\right)-2\left(x+3\right)=12\)
\(\Leftrightarrow5x-30-2x-6=12\)
\(\Leftrightarrow3x-36=12\)
\(\Leftrightarrow3x=48\Leftrightarrow x=16\)
c) \(3\left(x-4\right)-\left(8-x\right)=12\)
\(\Leftrightarrow3x-12-8+x=12\)
\(\Leftrightarrow4x-20=12\)
\(\Leftrightarrow4x=32\Leftrightarrow x=8\)
d) \(-7\left(3x-5\right)+2\left(7x-14\right)=28\)
\(\Leftrightarrow-21x+35+14x-28=28\)
\(\Leftrightarrow-7x+35=0\Leftrightarrow x=5\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a ) Ta có : 4(x - 5) - 3(x + 7) = -19
<=> 4x - 20 - 3x - 21 = -19
=> x - 41 = -19
=> x = -19 + 41
=> x = 22
b) Ta có " 7(x - 3) - 5(3 - x) = 11x - 5
<=> 7x - 21 - 15 + 5x = 11x - 5
<=> 12x - 36 = 11x - 5
=> 12x - 11x = -5 + 36
=> x = 31
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(x-1\right)⋮\left(x+5\right)\)
\(\Rightarrow\left[\left(x+5\right)-6\right]⋮\left(x+5\right)\) mà \(\left(x+5\right)⋮\left(x+5\right)\)
\(\Rightarrow6⋮\left(x+5\right)\)
\(\Rightarrow\left(x+5\right)\in\left\{1;2;3;6;-1;-2;-3;-6\right\}\)
\(\Rightarrow x\in\left\{6;7;8;11;4;3;2;-1\right\}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
=> |-2x + 3 |.|5 + 4x| = 19
vì |-2x + 3 |.|5 + 4x| lớn hơn hoặc bằng 0
=> x,0 <=> x<15
mà x>19 ko hợp lý
=> các số nguyên x thỏa mãn là 0
=> |-2x + 3 |.|5 + 4x| = 19
vì |-2x + 3 |.|5 + 4x| lớn hơn hoặc bằng 0
=> x,0 <=> x<15
mà x>19 (vô lý)
=> các số nguyên x thỏa mãn là 0
![](https://rs.olm.vn/images/avt/0.png?1311)
15+2x+3.5+4x=19
15+2x+4x+3.5=19
15+6x+15 =19
15+6x =19-15
15+6x = 14
6x = 14-15
6x = -1
x = -1 . 6
x = -6
15+2x+3.5+4x=19
15+2x+4x+3.5=19
15+6x+15 =19
15+6x =19-15
15+6x = 14
6x = 14-15
6x = -1
x = -1 . 6
x = -6
![](https://rs.olm.vn/images/avt/0.png?1311)