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Find the solution of the system of equations. 9x - 9y = -9 and 3x + 9y = -15

1 Answer

7 votes

Answer:

(-2 , -1)

Explanation:


\begin{cases}9x-9y=-9&\left(1 \right) \\ 3x+9y=-15&\left( 2\right) \end{cases}


\Longleftrightarrow \begin{cases}9x-9y=-9&\left( 1\right) \\ 12x=-24&\left( 1\right) +(2)\end{cases}


\Longleftrightarrow \begin{cases}x-y=-1&\left( 1\right) \\ x=-2&\left( 1\right) +(2)\end{cases}


\Longleftrightarrow \begin{cases}y=x+1=-2+1=-1&\left( 1\right) \\ x=-2&\left( 1\right) +(2)\end{cases}

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