c: ta có: \(7x^2-2x-5=0\)

\(\Leftrightarrow\left(x-1\right)\left(7x+5\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{5}{7}\end{matrix}\right.\)

\(x\inƯC\left(120;150\right)\)

mà x>12

nên \(x\in\left\{15;30\right\}\)

\(\left|x+1\right|=x\left(đk:x\ge0\right)\)

\(\Leftrightarrow x+1=x\)

\(\Leftrightarrow1=0\left(VLý\right)\)

Vậy \(S=\varnothing\)

\(|x+1|=x\) (đk: \(x\ge-1\))

<=> \(\left[{}\begin{matrix}x+1=x\\x+1=-x\end{matrix}\right.\)

<=> \(\left[{}\begin{matrix}0=-1\left(VLí\right)\\x=\dfrac{-1}{2}\left(TM\right)\end{matrix}\right.\)

Vậy nghiệm PT là \(S=\left\{\dfrac{-1}{2}\right\}\)

4x - 15 = - 75 - x

=> 4x + x = - 75 + 15

=> 5x = - 60

=> x = - 12

vậy_

72 - 3x = 5x + 8

=> - 3x - 5x = 8 - 72

=> - 8x = - 64

=> x = 8

vậy_

\(4x-15=-75-x\)

\(\Leftrightarrow4x+x=-75+15\)

\(\Leftrightarrow5x=-60\Leftrightarrow x=-12\)

không biết

30x75=2250

30*75=2250

Ko biết 

à mà bạn chém hộ cái 

\(4x-15=75-x\)

\(\text{ }-75-x=-\left(x+75\right)\)

\(4x-15=-\left(x+75\right)\)

\(4x-15=-x-75\)

\(5x=-60\)

\(5x=5.\left(-12\right)\)

\(x=-12\)

Trả lời:

4x -15 = -75 - x

=> 4x + x = -75 + 15

=> 5x = -60

=> x = -60 : 5

=> x = -12

\(4x-15=-75+3x\)

\(4x-3x=-75+15\)

             \(x=-60\)

mik chịu!!!!

chịu thui

=x+4x=-15+20

5x=5

=>x=1

x + 15 = 20 - 4x

=> x + 4x = 20 - 15

=> 5x = 5

=> x = 1

Vậy ...

=> x + 4x  = 20  - 15

=> 5x  = 5

=> x= 1

hok tốt