My Math Forum  

Go Back   My Math Forum > High School Math Forum > Algebra

Algebra Pre-Algebra and Basic Algebra Math Forum


Thanks Tree3Thanks
  • 1 Post By greg1313
  • 2 Post By v8archie
Reply
 
LinkBack Thread Tools Display Modes
June 13th, 2018, 08:08 AM   #1
Senior Member
 
Joined: Oct 2013
From: New York, USA

Posts: 622
Thanks: 85

Solve This Equation For xy

3x^2 + xy = 2y^2

Can you solve for xy?
EvanJ is offline  
 
June 13th, 2018, 09:37 AM   #2
Global Moderator
 
greg1313's Avatar
 
Joined: Oct 2008
From: London, Ontario, Canada - The Forest City

Posts: 7,884
Thanks: 1088

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
greg1313 is offline  
June 13th, 2018, 10:25 AM   #3
Math Team
 
Joined: Oct 2011
From: Ottawa Ontario, Canada

Posts: 13,600
Thanks: 954

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
Denis is offline  
June 13th, 2018, 04:48 PM   #4
Math Team
 
Joined: Dec 2013
From: Colombia

Posts: 7,511
Thanks: 2514

Math Focus: Mainly analysis and algebra
Quote:
Originally Posted by greg1313 View Post
$$(3x-2y)(x+y)=0\implies 3x=2y,x=-y$$
The left hand equation doesn't imply that both right hand equations hold.
Thanks from greg1313 and EvanJ
v8archie is offline  
Reply

  My Math Forum > High School Math Forum > Algebra

Tags
equation, solve



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Solve the equation... boomer029 Algebra 8 March 17th, 2012 06:09 PM
Solve Equation ijkm Abstract Algebra 1 March 15th, 2012 02:13 AM
Solve equation Valar30 Algebra 2 March 11th, 2011 07:47 PM
How can I solve this equation? Begtostudy Linear Algebra 3 July 29th, 2010 07:11 PM





Copyright © 2018 My Math Forum. All rights reserved.