How do you solve the following system: $3x - 4y = -23, 6x + 7y = -9$ ?

Question

2106 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-05-07T03:13:42

$(-3/2, 37/8)$

$[1] 3x - 4y = -23$
$[2] 6x + 7y = -9$

Get the equivalent of either variable from either equation.
For example, get the equivalent of $x$ from $[1]$

$3x - 4y = -23$
$=> 3x = 4y -23$
$=> x = (4y - 23)/3$

Substitute the obtained equivalent of the desired variable into the other equation.

$6x + 7y = -9$

$=> 6((4y - 23)/3) + 7y = -9$

$=> 2(4y - 23) = -9$

$=> 8y - 46 = -9$

$=> 8y = 37$

$=> y = 37/8$

Solve for the other variable now that we know the value of one variable

$3x - 4y = -23$

$=> 3x - 4(37/8) = -23$

$=> 3x - 37/2 = -23$

$=> 6x - 37 = -46$

$=> 6x = -9$

$=> x = -9/6 = -3/2$

How do you solve the following system: 3x - 4y = -23, 6x + 7y = -9 3x - 4y = -23, 6x + 7y = -9 ?