Giải thích các bước giải:
\(\begin{array}{l}
B1:\\
a.\left\{ \begin{array}{l}
y = 2 - 4x\\
8x + 6 - 12x = 5
\end{array} \right. \to \left\{ \begin{array}{l}
x = \frac{1}{4}\\
y = 1
\end{array} \right.\\
b.\left\{ \begin{array}{l}
y = \frac{{2x - 11}}{2}\\
4x - \frac{{10x - 55}}{2} = 3
\end{array} \right. \to \left\{ \begin{array}{l}
x = \frac{{49}}{2}\\
y = 19
\end{array} \right.\\
c.\left\{ \begin{array}{l}
y = 4 - 2x\\
5x - 16 + 8x = 3
\end{array} \right. \to \left\{ \begin{array}{l}
x = \frac{{19}}{{13}}\\
y = \frac{{14}}{{13}}
\end{array} \right.\\
d.\left\{ \begin{array}{l}
5x + 5y = 4x - 3\\
14x + 42y = 15 - 9y
\end{array} \right. \to \left\{ \begin{array}{l}
x = - 3 - 5y\\
- 42 - 70y + 51y = 15
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = - 3\\
x = 12
\end{array} \right.\\
e.\left\{ \begin{array}{l}
3x + 3y = 5x - 5y\\
x = 2y + 4
\end{array} \right. \to \left\{ \begin{array}{l}
4y + 8 - 8y = 0\\
x = 2y + 4
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = 2\\
x = 8
\end{array} \right.\\
f.\left\{ \begin{array}{l}
25x - 6y = 285\\
8x + 3y = 42
\end{array} \right. \to \left\{ \begin{array}{l}
y = \frac{{42 - 8x}}{3}\\
25x - 84 + 16x = 285
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = 9\\
y = - 10
\end{array} \right.
\end{array}\)
