View Question
 Question
 Subject: math Category: Reference, Education and News > Homework Help Asked by: dj2965-ga List Price: \$5.00 Posted: 04 Dec 2005 14:03 PST Expires: 03 Jan 2006 14:03 PST Question ID: 601366
 ```q-4000 / q +4000 how do you slove it?``` Request for Question Clarification by answerguru-ga on 04 Dec 2005 16:29 PST ```Hi there, The only way to solve for a variable is if it is part of an equation. Is there something missing in your original question?```
 There is no answer at this time.

 ```Answerguru is correct - but you can simplify this expression as follows. The key is reproducing what you have on the bottom in the top. (q-4000) / (q+4000) = (q+4000-8000) / (q+4000) = [(q+4000) / (q+4000)] - [8000 / (q+4000)] = 1 - [8000 / (q+4000)] Note that in the above, the square brackets [ ] are unnecessary under standard rules but have been added for clarity.```
 ```Maybe this is not an equation but a function? E.g. F(q) = (q-4000) / (q+4000). If so F can be calculated depending on the value of q. E.g.: F(5000) = (5000-4000)/(5000+4000) = 1000/9000 = 1/9. F(6000) = 2/10 = 1/5```
 ```For completeness we should show how to solve for q, given a specific value of F(q): Let (q-4000) / (q+4000) = c. Then q - 4000 = c (q + 4000) => q - 4000 = cq + 4000c => q - cq = 4000 c + 4000 => q (1-c) = 4000 (c+1) => q = 4000 (c+1)/(1-c), where c is not equal to 1. Obviously c = 1 is not allowed since this implies q - 4000 = q + 4000, which can never be true.```
 ```there's another trick,which in this particular question won't get you anywhere,but still its a good tricks on a difential and integeral maths (on the Limits' field) : (q-4000)/(q+4000) = =(q-4000)*(q+4000)/(q+4000)*(q+4000)= At this case ,its not that make any differences,but if the case was the opposites,which 'q-4000' may be negetive,and could gives a zero which undifiend,then this trick would help. hope I get you and others a proper answered```