جواب کار در کلاس صفحه 110 درس 6 ریاضی نهم (خط و معادله های خطی)

1

\(\begin{array}{l}\begin{array}{*{20}{c}}{2 \times }\\{}\\{}\end{array}\left\{ \begin{array}{l}x - y = 3\\\\4x + 2y = 6\end{array} \right. \Rightarrow \left\{ \begin{array}{l}2x - 2y = 6\\\\4x + 2y = 6\end{array} \right.\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\overline {6x = 12 \Rightarrow x = 2} \\\\2 - y = 3 \Rightarrow y = - 1\end{array}\)

2

\(\begin{array}{l}\begin{array}{*{20}{c}}{ - 2 \times }\\{}\\{3 \times }\end{array}\left\{ \begin{array}{l}3x - 5y = 1\\\\2x + 3y = 7\end{array} \right. \Rightarrow \left\{ \begin{array}{l} - 6x + 10y = - 2\\\\6x + 9y = 21\end{array} \right.\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\overline {19y = 19 \Rightarrow y = 1} \\\\3x - 5(1) = 1 \Rightarrow 3x = 6 \Rightarrow x = 2\end{array}\)

3

\(\begin{array}{l}\begin{array}{*{20}{c}}{ - 1 \times }\\{}\\{}\end{array}\left\{ \begin{array}{l}3x + 2y = 50\\\\2x + 2y = 35\end{array} \right. \Rightarrow \left\{ \begin{array}{l} - 3x - 2y = - 50\\\\2x + 2y = 35\end{array} \right.\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\overline { - x = - 15 \Rightarrow x = 15} \\\\3(15) + 2y = 50 \Rightarrow 2y = 5 \Rightarrow y = \frac{5}{2}\end{array}\)