May 9th, 2018, 01:52 PM  #1 
Member Joined: Nov 2016 From: Ireland Posts: 84 Thanks: 3  Tricky transposition problem
Hi guys, I'm working on a circuit problem here. I've changed these variables to make them more mathish... if such a word exists. I seem to have got myself in a terrible web here, that I can't get out of. At the moment, I'm here: 1 / xy = z + 1 / w I need it to be in a form something like X = w + yz or x = w + (y+z) In case you haven't guessed, this x is a total impedance and the w y z are an rlc circuit. But no matter, the math is the same. I feel like there's a piece of math I'm missing, a mathematical tool as such... What to do with that y? is my problem, without disturbing the rest of the equation. I've tried all sorts of things but just banging my head against the wall at this point. Last edited by skipjack; May 9th, 2018 at 06:31 PM. 
May 9th, 2018, 01:59 PM  #2 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 12,421 Thanks: 832  
May 9th, 2018, 03:44 PM  #3 
Member Joined: Nov 2016 From: Ireland Posts: 84 Thanks: 3  
May 9th, 2018, 04:11 PM  #4 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 12,421 Thanks: 832 
Please answer my question.

May 9th, 2018, 04:35 PM  #5 
Member Joined: Nov 2016 From: Ireland Posts: 84 Thanks: 3 
I did try to Denis. I'm not really sure what you mean by the question. As far as I'm aware z + (1 / w) is not equalled to (z+1) / w So to my mind you're basically asking the question  should 4 be 7? No... Unless you're about to open up some philosophical debate, then I suppose my answer must be  maybe... 
May 9th, 2018, 04:38 PM  #6  
Math Team Joined: May 2013 From: The Astral plane Posts: 1,797 Thanks: 715 Math Focus: Wibbly wobbly timeywimey stuff.  Quote:
So we now have 1/ x  y = z + (1/w). What is the LHS? (1/x)  y or 1/(x  y)? Dan  
May 9th, 2018, 05:01 PM  #7 
Member Joined: Nov 2016 From: Ireland Posts: 84 Thanks: 3 
Ahh ok sorry guys, I was off sick on `common sense` dispensing day LHS = 1 / (xy) RHS = z + (1/w) That pic up there ^ is what I'm actually trying to do. 
May 9th, 2018, 06:03 PM  #8 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 12,421 Thanks: 832  
May 9th, 2018, 06:28 PM  #9 
Global Moderator Joined: Dec 2006 Posts: 18,962 Thanks: 1606 
You have 1/(x  y) = z + 1/w, so x = y + 1/(z + 1/w). The righthand side of that can be rearranged in various ways. Changing the lefthand side further should be unnecessary, as it's already what you want. You mentioned trying "several bouts of rearranging", but you didn't post the full details. I suspect you did the rearranging incorrectly. Assuming that you've made some slips, how do we know that your original equation is correct? 
May 9th, 2018, 07:25 PM  #10 
Member Joined: Nov 2016 From: Ireland Posts: 84 Thanks: 3 
Sigh I don't know at this stage... Really I don't, I asked a question a number of days ago on another forum. This was the question: How did he get from here to there? Now you'd have thought that would have been a simple enough question, right? Wrong... Since then I've been on about a 2 day mission, on various errands, trying to find out. Apparently if I figure out the first equation in the first picture I posted, then I will receive enlightenment... Now since my journey began, some days ago  I don't know if I've got it my equations wrong, though I don't think so, or the guy on the other forum, would have shouted at me already. I'm at that point in the pic, the middle bit 1/(Ztjwl) = jwc + (1/R) All I want to do is get that (jwl) over to the RHS Please help!!! 

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