
Algebra PreAlgebra and Basic Algebra Math Forum 
 LinkBack  Thread Tools  Display Modes 
February 9th, 2013, 08:38 AM  #1 
Senior Member Joined: Sep 2010 From: Oslo, Norway Posts: 162 Thanks: 2  What is the correct way to apply quadratic formula?
Hello, I have this equation which I want to solve for variable : This is the Quadratic equation which I was taught in school: So I substitute the a, b and c: The problem is that Wolfram Alpha says the above is incorrect, and this is correct: Click here to see the solution at Wolfram Alpha I would like to learn why Wolfram Alpha is saying this. What do you think? Thank you for your time. Kind regards, Marius 
February 9th, 2013, 09:13 AM  #2 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 520 Math Focus: Calculus/ODEs  Re: What is the correct way to apply quadratic formula?
You need to put your equation in standard form first: Now, you can see: 
February 9th, 2013, 09:59 AM  #3 
Senior Member Joined: Sep 2010 From: Oslo, Norway Posts: 162 Thanks: 2  Re: What is the correct way to apply quadratic formula?
Thanks.M

February 9th, 2013, 06:09 PM  #4  
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 14,117 Thanks: 1002  Re: What is the correct way to apply quadratic formula? Quote:
2y = 2vtk  gt^2 Then: gt^2  2vkt + 2y = 0 Get my drift?  
February 12th, 2013, 05:28 AM  #5  
Senior Member Joined: Sep 2010 From: Oslo, Norway Posts: 162 Thanks: 2  Re: What is the correct way to apply quadratic formula? Quote:
I was looking at the dimensions in the result, and I cannot get them to match. This looks right What about this? Everything but the one m cancel out, and I am left with: Where did I go wrong? Thanks M  
February 12th, 2013, 06:21 AM  #6 
Global Moderator Joined: Dec 2006 Posts: 20,370 Thanks: 2007 
You incorrectly replaced "±" with "*" early on.

February 12th, 2013, 06:34 AM  #7 
Senior Member Joined: Sep 2010 From: Oslo, Norway Posts: 162 Thanks: 2  Re: What is the correct way to apply quadratic formula?
Skipjack, thank you so much! Now everything works out in my lovely mathematics Thank you!M 
February 13th, 2013, 04:48 AM  #8 
Senior Member Joined: Sep 2010 From: Oslo, Norway Posts: 162 Thanks: 2  Re: What is the correct way to apply quadratic formula?
Another question: When I am picking , and , I have the choice to pick the inverted set of numbers, because the right hand side of the standard form is 0 anyway. Are there any implications of doing this? I think so, at least it seems that for one set of numbers I may end up with a complex number as the result, but not in the other. For example, I suspect in the case of: may not always be equal to in the case of: Is this the case? If so, what is the correct way to pick the sign of , and ? Thank you for your time. Kind regards, Marius 
February 13th, 2013, 05:52 AM  #9 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,923 Thanks: 1123 Math Focus: Elementary mathematics and beyond  Re: What is the correct way to apply quadratic formula? 
February 13th, 2013, 06:02 AM  #10  
Senior Member Joined: Sep 2010 From: Oslo, Norway Posts: 162 Thanks: 2  Re: What is the correct way to apply quadratic formula? Quote:
 

Tags 
apply, correct, formula, quadratic 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
De Moivre's formula apply here?  WWRtelescoping  Complex Analysis  2  March 2nd, 2014 10:13 PM 
How to Apply the Shapley Value Formula?  Aqil  Economics  0  December 14th, 2012 11:31 AM 
Quadratic formula  Danicus  Algebra  8  March 27th, 2012 10:06 AM 
Quadratic Formula  johnny  Algebra  3  July 30th, 2008 08:55 AM 
Quadratic Formula  mathkid  Calculus  0  December 31st, 1969 04:00 PM 