My Math Forum Solve This Equation For xy

 Algebra Pre-Algebra and Basic Algebra Math Forum

 June 13th, 2018, 07:08 AM #1 Senior Member   Joined: Oct 2013 From: New York, USA Posts: 619 Thanks: 83 Solve This Equation For xy 3x^2 + xy = 2y^2 Can you solve for xy?
 June 13th, 2018, 08:37 AM #2 Global Moderator     Joined: Oct 2008 From: London, Ontario, Canada - The Forest City Posts: 7,879 Thanks: 1087 Math Focus: Elementary mathematics and beyond Hi EvanJ. $$3x^2 + xy = 2y^2$$ $$3x^2+xy-2y^2=0$$ $$(3x-2y)(x+y)=0\implies 3x=2y,x=-y$$ $$3x^2=2xy$$ $$xy=-y^2$$ Now sub into the original equation and take it from there. Thanks from EvanJ
 June 13th, 2018, 09:25 AM #3 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 13,315 Thanks: 935 Using quadratic: solve for x : x = -y or x = 2y/3 solve for y : y = -x or y = 3x/2 Just trying to cause confusion
June 13th, 2018, 03:48 PM   #4
Math Team

Joined: Dec 2013
From: Colombia

Posts: 7,445
Thanks: 2499

Math Focus: Mainly analysis and algebra
Quote:
 Originally Posted by greg1313 $$(3x-2y)(x+y)=0\implies 3x=2y,x=-y$$
The left hand equation doesn't imply that both right hand equations hold.

 Tags equation, solve

 Thread Tools Display Modes Linear Mode

 Similar Threads Thread Thread Starter Forum Replies Last Post boomer029 Algebra 8 March 17th, 2012 05:09 PM ijkm Abstract Algebra 1 March 15th, 2012 01:13 AM Valar30 Algebra 2 March 11th, 2011 06:47 PM Begtostudy Linear Algebra 3 July 29th, 2010 06:11 PM

 Contact - Home - Forums - Cryptocurrency Forum - Top