# Thread: how to isolate y?

1. ## how to isolate y?

I feel like a total idiot asking this question but how do you isolate y? I though this was easy but apparently my brain has left the building...

$y^2-3y-3=0$

how do you get to this???

$y=\frac{\pm 3 \sqrt{21}}{2}$

2. Quadratic formula

edit: or completing the square

3. lol... I am doing this in the context of some substitutions for x and y and have apparently confused myself to the point of forgetting how to solve a quadratic equation... nice.