My Math Forum Tricky transposition problem

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 May 9th, 2018, 02:52 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 / x-y = 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 07:31 PM.
May 9th, 2018, 02:59 PM   #2
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Quote:
 Originally Posted by Kevineamon 1 / x-y = z + 1 / w
should left side be: 1 / (x-y) ?

should right side be (z+1) / w ?

 May 9th, 2018, 04:44 PM #3 Member   Joined: Nov 2016 From: Ireland Posts: 84 Thanks: 3
 May 9th, 2018, 05:11 PM #4 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 13,782 Thanks: 970 Please answer my question. Thanks from Kevineamon
 May 9th, 2018, 05:35 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, 05:38 PM   #6
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Quote:
 Originally Posted by Kevineamon 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...
He's merely asking you to provide parenthesis so we know what those expressions actually are.

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, 06:01 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 / (x-y) RHS = z + (1/w) That pic up there ^ is what I'm actually trying to do. Thanks from topsquark
May 9th, 2018, 07:03 PM   #8
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Quote:
 Originally Posted by Kevineamon LHS = 1 / (x-y) RHS = z + (1/w)
1 / (x-y) = z + (1/w)

Solving for x:
x = (w + y + wyz) / (wz + 1)

 May 9th, 2018, 07:28 PM #9 Global Moderator   Joined: Dec 2006 Posts: 20,089 Thanks: 1902 You have 1/(x - y) = z + 1/w, so x = y + 1/(z + 1/w). The right-hand side of that can be rearranged in various ways. Changing the left-hand 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, 08:25 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/(Zt-jwl) = jwc + (1/R) All I want to do is get that (-jwl) over to the RHS Please help!!!

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