# Mathematical Simplification

• January 31st 2010, 10:29 AM
aktor
Mathematical Simplification
Hello all. I was working through an example in my Physics book and am having trouble with the simplifying algebra (very rusty). I'll go ahead and skip forward to the step that's giving me trouble:

E = q/(4πεz^2) [ 1/(1-(d/2z))^2 - 1/(1+(d/2z))^2 ]

Sorry that's so hard to read on here. I basically need to find a common denominator and multiply everything through. It should eventually reduce to:

E = (1/2πε) qd/z^3

Thanks for your help!
• January 31st 2010, 10:52 AM
VonNemo19
Quote:

Originally Posted by aktor
Hello all. I was working through an example in my Physics book and am having trouble with the simplifying algebra (very rusty). I'll go ahead and skip forward to the step that's giving me trouble:

E = q/(4πεz^2) [ 1/(1-(d/2z))^2 - 1/(1+(d/2z))^2 ]

Sorry that's so hard to read on here. I basically need to find a common denominator and multiply everything through. It should eventually reduce to:

E = (1/2πε) qd/z^3

Thanks for your help!

LCD:

$(1-\frac{d}{2z})^2(1+\frac{d}{2z})^2$

So, $\frac{q}{4\pi\epsilon{z}^2}\left[\frac{(1+\frac{d}{2z})^2-(1-\frac{d}{2z})^2}{(1-\frac{d}{2z})^2(1+\frac{d}{2z})^2}\right]$
• January 31st 2010, 12:00 PM
aktor
Thanks! Temporary brain lapse.
• January 31st 2010, 12:02 PM
VonNemo19
Quote:

Originally Posted by aktor
Thanks! Temporary brain lapse.

So, can you finish then?
• January 31st 2010, 12:22 PM
aktor
Yeah. That was what I originally did, but when I looked back at my work I found a mistake that threw everything off at the end. Thanks for your quick reply.