How do you solve $y = 3 x - 9$ $y=3x-9$ and $2 y - 6 x = - 18$ $2y-6x=-18$ using substitution?

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Answer 1 · 2017-07-17T16:58:20

$y = 3 x - 9$ $y=3x-9$
$2 y - 6 x = - 18$ $2y-6x=-18$

$y = 3 x - 9 \to 1$ $y=3x-9 rarr color(blue)1$
$2 y - 6 x = - 18 \to 2$ $2y-6x=-18 rarr color(red)2$

$2 (3 x - 9) - 6 x = - 18$ $2(3x-9)-6x=-18$

$2 (3 x - 9) - 6 x = - 18$ $2(3x-9)-6x=-18$
$6 x - 18 - 6 x = - 18$ $6x-18-6x=-18$
$6 x - 6 x = - 18 + 18$ $6x-6x=-18+18$
$0 = 0$ $0=0$

As you may have realised, those simultaenous equations are undefined. Try checking if you got any errors while copying this question.

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How do you solve y=3x−9y=3x-9 and 2y−6x=−182y-6x=-18 using substitution?