My Math Forum  

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

Algebra Pre-Algebra and Basic Algebra Math Forum


Thanks Tree2Thanks
  • 2 Post By v8archie
Reply
 
LinkBack Thread Tools Display Modes
May 3rd, 2014, 04:38 AM   #1
Newbie
 
Joined: May 2014
From: UK

Posts: 4
Thanks: 0

Parabolas

Hello there, I've got the following problem that I require some help with:

x^2-3y-4=0, I need to find all values of (x,y) that are integers. Has anybody got any ideas?

Ty in advance, Bearz
Bearz is offline  
 
May 3rd, 2014, 05:54 AM   #2
Math Team
 
Joined: Dec 2013
From: Colombia

Posts: 7,640
Thanks: 2624

Math Focus: Mainly analysis and algebra
$$y = \frac{1}{3}(x - 2)(x + 2)$$
Thus, given $x \in \mathbb{Z}$, $x - 2 = 3k$ and $x+2 =3k$ ($k \in \mathbb{Z}$) give $y \in \mathbb{Z}$.

So, all $x = 3k \pm 2$ are integer solutions which is the same as saying all integers not divisible by three.

We can also investigate the $y$ values.
$$y = k(3k \pm 4) = 3k^2 \pm 4k$$
Thanks from Olinguito and Bearz

Last edited by v8archie; May 3rd, 2014 at 06:05 AM.
v8archie is offline  
Reply

  My Math Forum > High School Math Forum > Algebra

Tags
parabolas



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
I NEED HELPPP PLEASEEEEE (parabolas) sumi123 Algebra 2 August 5th, 2012 10:26 AM
quadratics and parabolas anthonye Algebra 3 May 8th, 2012 05:52 AM
Question about parabolas jkh1919 Algebra 1 September 25th, 2011 08:15 PM
Parabolas sallyyy Algebra 3 November 14th, 2010 10:46 AM
Conics: Parabolas... ILoveISO Algebra 11 November 23rd, 2009 08:44 PM





Copyright © 2019 My Math Forum. All rights reserved.