How do you solve y = 2x + 9 and 2x - y = -9?

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Answer 1 · 2015-11-07T17:04:40

There are infinite possible solutions because the equations are the same.

You have the equations:
$1 : y = 2 x + 9$ $1: y=2x + 9$
$2 : 2 x - y = - 9$ $2:2x - y = -9$

Let's try to play around with the second one...
$2 x - y = - 9$ $2x - y = -9$
$- y = - 9 - 2 x$ $-y = -9 -2x$
$y = 2 x + 9$ $y = 2x + 9$

You get the same equation as the first one!

If you plot those into the same coordinate system, you see that there are an infinite amount of possible solves.