Đáp án:

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Giải thích các bước giải:

a)

$|x+3|-7=3x$

$|x+3|=3x+7$

TH1: $x+3=3x+7$

$x-3x=7-3$

$-2x=4$

$x=-2$

TH2: $x+3=-3x-7$

$x+3x=-7-3$

$4x=-10$

$x=\frac{-10}{4}$

$x=\frac{-5}{2}

Vậy $x=-2$ hoặc $x=\frac{-5}{2}$

b)

$|x-5|-3x=19$

$|x-5|=19+3x$

TH1: $x-5=19+3x$

$x-3x=19+5$

$-2x=24$

$x=-12$

TH2: $x-5=-19-3x$

$x+3x=-19+5$

$4x=-14$

$x=\frac{-14}{4}$

$x=\frac{-7}{2}$

Vậy $x=-12$ hoặc $x=\frac{-7}{2}$

c)

$|3-x|-3x=11$

$|3-x|=11+3x$

TH1: $3-x=11+3x$

$-x-3x=11-3$

$-4x=8$

$x=-2$

TH2: $3-x=-11-3x$

$-x+3x=-11-3$

$2x=-14$

$x=-7$

Vậy $x=-2$ hoặc $x=-7$

a, $| x+3|-7= 3x$

⇔ $| x+3|= 3x+7$

⇔ \(\left[ \begin{array}{l}x+3=3x+7\\x+3= -3x-7\end{array} \right.\)

⇔ \(\left[ \begin{array}{l}x=2\\x=-2,5\end{array} \right.\) 

Vậy ...

b, $| x-5|-3x= 19$

⇔ $|x-5|= 19+3x$

⇔ \(\left[ \begin{array}{l}x-5=19+3x\\x-5= -19-3x\end{array} \right.\)

⇔ \(\left[ \begin{array}{l}x=-12\\x=-3,5\end{array} \right.\) 

Vậy ...

c, $| 3-x|-3x= 11$

⇔ $|3-x|= 11+3x$

⇔ \(\left[ \begin{array}{l}3-x= 11+3x\\3-x= -11-3x\end{array} \right.\)

⇔ \(\left[ \begin{array}{l}x=-2\\x=-7\end{array} \right.\) 

Vậy ...