How do you use the substitution method to solve 3x-15y=-12 and 3x+24y=-12?

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How do you use the substitution method to solve 3x-15y=-12 and 3x+24y=-12?

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Answer 1 · 2015-06-26T22:38:49

Derive an expression for $3 x$ $3x$ from the first equation, then substitute that in the second equation and solve to find $y = 0$ $y = 0$ and $x = - 4$ $x = -4$

Explanation:

First add $15 y$ $15y$ to both sides of the first equation to get:

[1] $3 x = 15 y - 12$ $3x=15y-12$

Then substitute $15 y - 12$ $15y-12$ for $3 x$ $3x$ in the second equation to get:

$(15 y - 12) + 24 y = - 12$ $(15y-12)+24y=-12$

Add $12$ $12$ to both sides and combine the remaining terms to get:

$39 y = 0$ $39y = 0$

Divide both sides by $39$ $39$ to get $y = 0$ $y = 0$

Then substitute $y = 0$ $y=0$ in [1] to get:

$3 x = - 12$ $3x = -12$

Divide both sides by $3$ $3$ to get $x = - 4$ $x = -4$

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How do you use the substitution method to solve 3x-15y=-12 and 3x+24y=-12?

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