Вопрос:

Решите систему уравнений: y=3x-5; x^2+y^2=25.

Ответ:

\[\left\{ \begin{matrix} y = 3x - 5\ \ \ \\ x^{2} + y^{2} = 25 \\ \end{matrix} \right.\ \]

\[x^{2} + (3x - 5)^{2} = 25\]

\[x^{2} + 9x^{2} - 30x + 25 - 25 = 0\]

\[10x^{2} - 30x = 0\]

\[10x(x - 3) = 0\]

\[x_{1} = 0;\ \ \ \ \ x_{2} = 3.\]

\[x_{1} = 0 \Longrightarrow \ \ \ \ \ \ \ y_{1} = 3 \cdot 0 - 5 =\]

\[= 0 - 5 = - 5.\]

\[x_{2} = 3 \Longrightarrow \ \ \ \ \ \ \ y_{2} = 3 \cdot 3 - 5 =\]

\[= 9 - 5 = 4.\]

\[Ответ:(0;\ - 5),\ \ \ (3;4).\]

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