How do you solve x-y=0 and 12x-5y=-21?

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Answer 1 · 2015-10-14T06:33:16

The solution is
$x = - 3, y = - 3$ $color(blue)(x=-3,y=-3$

$x - y = 0$ $x-y=0$
$x = y$ $x=color(blue)(y$ ......equation $1$ $1$

$12 x - 5 y = - 21$ $12x-5y=-21$ ....equation $2$ $2$

Substituting $1$ $1$ in $2$ $2$

$12 x - 5 y = - 21$ $12x-5y=-21$

$12 \cdot (y) - 5 y = - 21$ $12* (color(blue)(y))-5y=-21$

$12 y - 5 y = - 21$ $12y-5y=-21$

$7 y = - 21$ $7y=-21$

$y = - \frac{21}{7}$ $y=-21/7$

$y = - 3$ $color(blue)(y=-3$

And since $x = y$ $x=y$
$x = - 3$ $color(blue)(x=-3$