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Find the ordered pair  that satisfies the system of equations
\begin{align*} x+3y &= -4,\\ 3x -7y &= 36. \end{align*}

Jun 28, 2021

#1
+234
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Multiply first equation by 3,

$$3x + 9y = -12$$

$$3x -7y = 36$$

Subtract,

$$16y = -48$$

$$y = -3$$

Plug y back into one of the equations,

$$x -9 = -4$$

$$x = 5$$

So (x, y) = (5, -3)

Jun 28, 2021
#2
+785
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$-9x - 27y = 36$

$3x - 7y = 36$

$3x - 7y = -9x - 27y$

$12x = -20y$

$3x = -5y$

$x = - \frac{5}{3} y$

$3x + 9y = -12$

$16y = -48$

$y = -3$

$x = 5$

$(x,y) = (5, -3)$

Jun 28, 2021