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 31st, 2014, 12:14 AM   #1
Newbie
 
Joined: May 2014
From: bangkok

Posts: 4
Thanks: 0

Help please

How do you solve

x+1 over x+3 =2x-1 over 3x + 1

Thanks
SeanBkk is offline  
 
May 31st, 2014, 02:22 AM   #2
Math Team
 
Joined: Oct 2011
From: Ottawa Ontario, Canada

Posts: 14,326
Thanks: 1023

Hint: if a/b = c/d, then ad = bc
Denis is offline  
May 31st, 2014, 06:18 PM   #3
Newbie
 
Joined: May 2014
From: Bangkok

Posts: 6
Thanks: 0

A little extra

x+1 over x+3 =2x-1 over 3x + 1

so, (x+1)(3x+1)(x+3)(2x-1)?

Sorry, to sound stupid I just can't expand it
Johninbkk71 is offline  
May 31st, 2014, 07:58 PM   #4
Math Team
 
Joined: Oct 2011
From: Ottawa Ontario, Canada

Posts: 14,326
Thanks: 1023

Are you posting under different names?
Denis is offline  
June 1st, 2014, 03:53 AM   #5
Senior Member
 
Joined: Jul 2013
From: United Kingdom

Posts: 471
Thanks: 40

$\displaystyle \frac { x+1 }{ x+3 } =\frac { 2x-1 }{ 3x+1 } \\ \\ \frac { x+1 }{ \left( x+3 \right) } -\frac { \left( 2x-1 \right) }{ \left( 3x+1 \right) } =0\\ \\ \frac { \left( x+1 \right) \left( 3x+1 \right) }{ \left( x+3 \right) \left( 3x+1 \right) } -\frac { \left( 2x-1 \right) \left( x+3 \right) }{ \left( x+3 \right) \left( 3x+1 \right) } =0\\ \\ \frac { 3{ x }^{ 2 }+x+3x+1-\left[ 2{ x }^{ 2 }+6x-x-3 \right] }{ \left( x+3 \right) \left( 3x+1 \right) } =0\\ \\ 3{ x }^{ 2 }+4x+1-\left[ 2{ x }^{ 2 }+5x-3 \right] =0\\ \\ 3{ x }^{ 2 }+4x+1-2{ x }^{ 2 }-5x+3=0\\ \\ { x }^{ 2 }-x+4=0\\ \\ { x }^{ 2 }-x=-4\\ \\ { \left( x-\frac { 1 }{ 2 } \right) }^{ 2 }-{ \left( \frac { 1 }{ 2 } \right) }^{ 2 }=-4\\ \\ { \left( x-\frac { 1 }{ 2 } \right) }^{ 2 }=-\frac { 15 }{ 4 } \\ \\ \therefore \quad No\quad solution.\\ \\ $

This can be seen on this graph: https://www.desmos.com/calculator/ogc8fwn2hl.

Last edited by perfect_world; June 1st, 2014 at 03:56 AM.
perfect_world is offline  
Reply

  My Math Forum > High School Math Forum > Algebra



Thread Tools
Display Modes






Copyright © 2019 My Math Forum. All rights reserved.