1. Jan 18, 2013

### peterpanhandle

1. The problem statement, all variables and given/known data

Solve 4y-y2=x for y.

3. The attempt at a solution

First I tried using the quadratic equation with a=-1 b=4 c=-x

y=(-b±(42-4(-1)(-x))(1/2))/2(-1)

That got me this far: y=2±(8-2x)(1/2)

Then I checked wolfram and now I am confused
y=±2-sqrt(4-x
. Did I not approach this corectly?

2. Jan 18, 2013

### vela

Staff Emeritus
Your approach is fine. You just made an algebra mistake while simplifying.

You had $y = \frac{-4 \pm \sqrt{16 - 4x}}{-2}$. Note that you can't simply divide the stuff inside the radical by 2 when you bring the 2 from the denominator inside.

3. Jan 20, 2013

### peterpanhandle

Thank you for the quick reply and sorry for my slow thanks. How very typical of me that it's some algebraic error Thanks again!

4. Jan 20, 2013

### SammyS

Staff Emeritus

As the originator of the thread, you don't really need to use a Spoiler.