Giải thích các bước giải:
\(\begin{array}{l}
d.\left\{ \begin{array}{l}
5x + 5y = 4x - 3\\
14x + 42y = 15 - 9y
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = - 3 - 5y\\
14\left( { - 3 - 5y} \right) + 51y = 15
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = - 3 - 5y\\
- 19y = 57
\end{array} \right. \to \left\{ \begin{array}{l}
y = - \frac{{57}}{{19}}\\
x = 12
\end{array} \right.\\
e.\left\{ \begin{array}{l}
3x + 3y = 5x - 5y\\
x = 2y + 4
\end{array} \right. \to \left\{ \begin{array}{l}
2\left( {2y + 4} \right) - 8y = 0\\
x = 2y + 4
\end{array} \right.\\
\to \left\{ \begin{array}{l}
- 4y + 8 = 0\\
x = 2y + 4
\end{array} \right. \to \left\{ \begin{array}{l}
y = 2\\
x = 8
\end{array} \right.\\
f.\left\{ \begin{array}{l}
25x - 6y = 285\\
8x + 3y = 42
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = \frac{{42 - 8x}}{3}\\
25x - 2\left( {42 - 8x} \right) = 285
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = \frac{{43}}{2}\\
y = - \frac{{130}}{3}
\end{array} \right.
\end{array}\)
