Решите систему уравнений:
а) $\begin{equation*}
\begin{cases}
\frac{x}{2} + \frac{y}{3} = 3, &\\
\frac{x}{3} + \frac{y}{2} = \frac{1}{3}; &
\end{cases}
\end{equation*}$
б) $\begin{equation*}
\begin{cases}
\frac{x}{3} + \frac{y}{2} = 5, &\\
5x - 11y = 1; &
\end{cases}
\end{equation*}$
в) $\begin{equation*}
\begin{cases}
\frac{x}{3} - \frac{y}{2} = -4, &\\
\frac{x}{2} + \frac{y}{4} = -2; &
\end{cases}
\end{equation*}$
г) $\begin{equation*}
\begin{cases}
4x + 7y = 1, &\\
\frac{x}{5} + \frac{y}{6} = -\frac{1}{2}. &
\end{cases}
\end{equation*}$
$\begin{equation*}
\begin{cases}
\frac{x}{2} + \frac{y}{3} = 3 |*6 &\\
\frac{x}{3} + \frac{y}{2} = \frac{1}{3} |*6 &
\end{cases}
\end{equation*}$
$\begin{equation*}
\begin{cases}
3x + 2y = 18 &\\
2x + 3y = 2 &
\end{cases}
\end{equation*}$
$\begin{equation*}
\begin{cases}
3x + 2y = 18 &\\
2x = 2 - 3y &
\end{cases}
\end{equation*}$
$\begin{equation*}
\begin{cases}
3x + 2y = 18 &\\
x = 1 - 1,5y &
\end{cases}
\end{equation*}$
3x + 2y = 18
3 * (1 − 1,5y) + 2y = 18
3 − 4,5y + 2y = 18
−2,5y = 18 − 3
−2,5y = 15
y = 15 : (−2,5)
y = −6
x = 1 − 1,5y = 1 − 1,5 * (−6) = 1 + 9 = 10
Ответ: (10;−6)
$\begin{equation*}
\begin{cases}
\frac{x}{3} + \frac{y}{2} = 5 | *6 &\\
5x - 11y = 1 &
\end{cases}
\end{equation*}$
$\begin{equation*}
\begin{cases}
2x + 3y = 30 &\\
5x - 11y = 1 &
\end{cases}
\end{equation*}$
$\begin{equation*}
\begin{cases}
2x = 30 - 3y &\\
5x - 11y = 1 &
\end{cases}
\end{equation*}$
$\begin{equation*}
\begin{cases}
x = 15 - 1,5y &\\
5x - 11y = 1 &
\end{cases}
\end{equation*}$
5x − 11y = 1
5 * (15 − 1,5y) − 11y = 1
75 − 7,5y − 11y = 1
−18,5y = 1 − 75
−18,5y = −74
y = −74 : (−18,5)
y = 4
x = 15 − 1,5y = 15 − 1,5 * 4 = 15 − 6 = 9
Ответ: (9;4)
$\begin{equation*}
\begin{cases}
\frac{x}{3} - \frac{y}{2} = -4 | *6 &\\
\frac{x}{2} + \frac{y}{4} = -2 | *4 &
\end{cases}
\end{equation*}$
$\begin{equation*}
\begin{cases}
2x - 3y = -24 &\\
2x + y = -8 &
\end{cases}
\end{equation*}$
$\begin{equation*}
\begin{cases}
2x - 3y = -24 &\\
y = -8 - 2x &
\end{cases}
\end{equation*}$
2x − 3 * (−8 − 2x) = −24
2x + 24 + 6x = −24
8x = −24 − 24
8x = −48
x = −48 : 8
x = −6
y = −8 − 2x = −8 − 2 * (−6) = −8 + 12 = 4
Ответ: (−6;4)
$\begin{equation*}
\begin{cases}
4x + 7y = 1 &\\
\frac{x}{5} + \frac{y}{6} = -\frac{1}{2} | *30 &
\end{cases}
\end{equation*}$
$\begin{equation*}
\begin{cases}
4x + 7y = 1 &\\
6x + 5y = -15 &
\end{cases}
\end{equation*}$
$\begin{equation*}
\begin{cases}
4x = 1 - 7y &\\
6x + 5y = -15 &
\end{cases}
\end{equation*}$
$\begin{equation*}
\begin{cases}
x = 0,25 - 1,75y &\\
6x + 5y = -15 &
\end{cases}
\end{equation*}$
6x + 5y = −15
6 * (0,25 − 1,75y) + 5y = −15
1,5 − 10,5y + 5y = −15
−5,5y = −15 − 1,5
−5,5y = −16,5
y = −16,5 : (−5,5)
y = 3
x = 0,25 − 1,75y = 0,25 − 1,75 * 3 = 0,25 − 5,25 = −5
Ответ: (−5;3)
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