My Math Forum  

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

Algebra Pre-Algebra and Basic Algebra Math Forum


Reply
 
LinkBack Thread Tools Display Modes
May 19th, 2015, 12:22 PM   #1
Senior Member
 
Joined: Jan 2015
From: London

Posts: 108
Thanks: 2

Extended Factorising

Hi can someone help me work out his equation

2x^2 + 7x - 4 = 0

Help Thanks
jamesbrown is offline  
 
May 19th, 2015, 12:27 PM   #2
Global Moderator
 
CRGreathouse's Avatar
 
Joined: Nov 2006
From: UTC -5

Posts: 16,046
Thanks: 938

Math Focus: Number theory, computational mathematics, combinatorics, FOM, symbolic logic, TCS, algorithms
Code:
factor(2*x^2 + 7*x - 4)
in PARI/GP yields
Code:
[  x + 4 1]

[2*x - 1 1]
that is, $2x^2+7x-4=(x+4)(2x-1)$.
CRGreathouse is offline  
May 19th, 2015, 12:31 PM   #3
Math Team
 
Joined: Dec 2013
From: Colombia

Posts: 7,634
Thanks: 2620

Math Focus: Mainly analysis and algebra
Any rational roots are of the form $a \over b$ where $a \in \{\pm1, \pm2, \pm4\}$ and $b \in \{\pm1, \pm2\}$ (these are the integer factors of the units term and the squared term respectively).

That means that a rational root $r$, (if it exists) is one of $\left\{ \pm\frac12, \pm1, \pm2, \pm 4\right\}$. You can test each of these using the factor theorem.

Last edited by v8archie; May 19th, 2015 at 12:36 PM.
v8archie is offline  
Reply

  My Math Forum > High School Math Forum > Algebra

Tags
extended, factorising



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Can set-valued mappings be extended? 03sqq Applied Math 1 January 31st, 2013 05:12 AM
Extended Mean Value Theorem chapsticks Calculus 2 June 30th, 2012 03:06 PM
Extended domain Zeta Agno Number Theory 2 May 30th, 2011 01:24 PM
extended euclidean algorithm tinynerdi Number Theory 1 August 29th, 2010 11:26 PM
Proth theorem extended leavemsg1 Number Theory 0 April 6th, 2009 07:01 AM





Copyright © 2019 My Math Forum. All rights reserved.