Đáp án:
$\begin{array}{l}
B2)a)\left| {x + 3} \right| = 15\\
\Leftrightarrow \left[ \begin{array}{l}
x + 3 = 15\\
x + 3 = - 15
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
x = 12\\
x = - 18
\end{array} \right.\\
Vậy\,x = 12;x = - 18\\
b)\left| {x - 7} \right| + 13 = 25\\
\Leftrightarrow \left| {x - 7} \right| = 12\\
\Leftrightarrow \left[ \begin{array}{l}
x - 7 = 12 \Leftrightarrow x = 19\\
x - 7 = - 12 \Leftrightarrow x = - 5
\end{array} \right.\\
Vậy\,x = 19;x = - 5\\
c)\left| {x - 3} \right| - 16 = - 4\\
\Leftrightarrow \left| {x - 3} \right| = 12\\
\Leftrightarrow \left[ \begin{array}{l}
x - 3 = 12 \Leftrightarrow x = 15\\
x - 3 = - 12 \Leftrightarrow x = - 9
\end{array} \right.\\
Vậy\,x = 15;x = - 9\\
d)26 - \left| {x + 9} \right| = - 13\\
\Leftrightarrow \left| {x + 9} \right| = 39\\
\Leftrightarrow \left[ \begin{array}{l}
x + 9 = 39 \Leftrightarrow x = 30\\
x + 9 = - 39 \Leftrightarrow x = - 48
\end{array} \right.\\
Vậy\,x = 30;x = - 48\\
B3)a)11x = 55\\
\Leftrightarrow x = \dfrac{{55}}{{11}} = 5\\
Vậy\,x = 5\\
b)12x = 144\\
\Leftrightarrow x = 144:12\\
\Leftrightarrow x = 12\\
Vậy\,x = 12\\
c) - 3x = - 12\\
\Leftrightarrow x = - 12:\left( { - 3} \right)\\
\Leftrightarrow x = 4\\
Vậy\,x = 4\\
d)0.x = 4\left( {ktm} \right)\\
Vậy\,x \in \emptyset \\
e)2x = 6\\
\Leftrightarrow x = 3\\
Vậy\,x = 3\\
B4)a)\left( {x + 5} \right)\left( {x - 4} \right) = 0\\
\Leftrightarrow x = - 5;x = 4\\
Vậy\,x = - 5;x = 4\\
b)\left( {x - 1} \right)\left( {x - 3} \right) = 0\\
\Leftrightarrow x = 1;x = 3\\
Vậy\,x = 1;x = 3\\
c)\left( {3 - x} \right)\left( {x - 3} \right) = 0\\
\Leftrightarrow x = 3\\
Vậy\,x = 3\\
d)x\left( {x + 1} \right) = 0\\
\Leftrightarrow x = 0;x = - 1\\
Vậy\,x = 0;x = - 1
\end{array}$
