
Algebra PreAlgebra and Basic Algebra Math Forum 
 LinkBack  Thread Tools  Display Modes 
August 25th, 2017, 02:50 AM  #1 
Member Joined: Jan 2014 Posts: 55 Thanks: 2  Quadratic Equations by Completing the Square
Hi, I'm working on this equation where (b/2)^2 = 8/2=4^2=16. However, I'm stuck where I think I need to square both sides, as you can see a purple star there. I also scratchy on how to factor x^2+4x+8? which the answer becomes in the end is in red. 2 plus or minus sq of 14 Last edited by skipjack; August 25th, 2017 at 06:55 AM. 
August 25th, 2017, 03:04 AM  #2 
Math Team Joined: Jul 2011 From: Texas Posts: 2,755 Thanks: 1405 
$2x^2+8x+1=0$ $2x^2+8x = 1$ $x^2+4x=\dfrac{1}{2}$ $x^2+4x+4 = \dfrac{1}{2} +4$ $(x+2)^2=\dfrac{7}{2}$ $x+2= \pm \sqrt{\dfrac{7}{2}}$ $x = 2 \pm \dfrac{\sqrt{14}}{2} = \dfrac{4 \pm \sqrt{14}}{2}$ 
August 25th, 2017, 08:33 PM  #3 
Member Joined: Jan 2014 Posts: 55 Thanks: 2 
Thank you! 
August 26th, 2017, 01:14 PM  #4 
Math Team Joined: Jan 2015 From: Alabama Posts: 3,191 Thanks: 871 
Your basic error was that you did not have $\displaystyle x^2+ 8x+ 1$ that you are trying to make a "complete square", you have $\displaystyle 2x^2+ 8x+ 1$ and that "2" multiplying $\displaystyle x^2$ makes all the difference. skeeter took care of that by first dividing the equation by 2.


Tags 
completing, equations, quadratic, square 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
quadratic and completing the square problem  taylor_1989_2012  Algebra  2  December 23rd, 2012 09:38 AM 
quadratic and completing the square issue  taylor_1989_2012  Algebra  5  November 1st, 2012 06:56 AM 
Solving Quadratic Equations by Completing the Square  watkd  Algebra  9  August 5th, 2012 09:59 PM 
Solve Quadratic Equations By Completing Square  watkd  Algebra  5  August 25th, 2010 10:43 AM 
completing the square or quadratic equation?  empiricus  Algebra  2  March 28th, 2010 01:52 PM 