# Thread: Realitvely Easy Question

1. ## Realitvely Easy Question

$
y = 2x
$

$
5 = x^2 + y^2
$

Alright guys, I missed a note, and im tryign to figure out what to do...

I beleive I use substitution, but im not quite sure how exactly. Can someone quicly run through it for me? Thanks guys.

2. $5=x^2+(2x)^2=x^2+4x^2=5x^2\Leftrightarrow x^2=1\Leftrightarrow x=\pm 1$

3. You are my hero.