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April 24th, 2015, 06:14 AM  #1 
Newbie Joined: Oct 2014 From: England Posts: 12 Thanks: 0  Logarithms and Simultaneous Equations
Hey This is part of C2 Alevel Maths from OCR (UK) I feel as though I figured this question out, but not entirely Solve the pair of simultaneous equations Log(yx)=0 and 2logy=log(21+x) So I did it this way I thought unlog the first one Makes it Yx=0 Then move the x to the right side Y=x And making that equation (1) So then I see the second equation 2log y And because of the exponential rule, I moved the 2 to make it a squared y Log y^2=log(21+x) Then I decided to unlog it y^2=21+x And making that equation (2) So I decided to substitute equation (1) into (2) x^2=21+x And move the 21+x to the left side x^2x21 However this seems unfactorisable. Am I doing it wrong? 
April 24th, 2015, 06:16 AM  #2 
Math Team Joined: Dec 2013 From: Colombia Posts: 7,674 Thanks: 2654 Math Focus: Mainly analysis and algebra  
April 24th, 2015, 07:17 AM  #3 
Newbie Joined: Oct 2014 From: England Posts: 12 Thanks: 0 
I don't understand what makes it wrong

April 24th, 2015, 07:23 AM  #4 
Math Team Joined: Jul 2011 From: Texas Posts: 3,002 Thanks: 1587  

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equations, logarithms, simultaneous 
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