Find all School-related info fast with the new School-Specific MBA Forum

It is currently 23 Oct 2014, 03:32

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Factoring quadratic equation

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Intern
Intern
avatar
Joined: 17 Jul 2013
Posts: 2
Followers: 0

Kudos [?]: 0 [0], given: 0

Factoring quadratic equation [#permalink] New post 04 Sep 2013, 09:49
Hi friends,

I´m had been problems to solve by factoring the next equation. (x^2)- 13x-130=0
Is there anyone who can help me to solve it?

Thanks in advance!
Expert Post
2 KUDOS received
Magoosh GMAT Instructor
User avatar
Joined: 28 Dec 2011
Posts: 2142
Followers: 539

Kudos [?]: 2273 [2] , given: 31

Re: Factoring quadratic equation [#permalink] New post 04 Sep 2013, 13:37
2
This post received
KUDOS
Expert's post
bandala wrote:
Hi friends,

I´m had been problems to solve by factoring the next equation. (x^2)- 13x-130=0
Is there anyone who can help me to solve it?

Thanks in advance!

Dear bandala,

First of all, here's a general article on the topic.
http://magoosh.com/gmat/2012/algebra-on ... to-factor/

For this question, we need two numbers
(a) whose product is -130, so one is positive and one is negative
and
(b) whose sum is -13 (so the one with the larger absolute value is negative)

130 = 13*10, but those two numbers are too close
130 = 5*26
130 = 2*65
Those are the only whole number factors that multiply to 130, and none of them work.

The problem is --- this quadratic is 100% unfactorable. The solutions involve expressions with the square-root of 689, which is an unsimplifiable square-root. The GMAT would NEVER ask you to factor such an equation. If this equation appeared in some form on the GMAT, it would have to be a question that could be solved without factoring it. The GMAT would not expect you to find the solutions without a calculator.

Does this make sense?
Mike :-)
_________________

Mike McGarry
Magoosh Test Prep

Image

Image

Intern
Intern
avatar
Joined: 17 Jul 2013
Posts: 2
Followers: 0

Kudos [?]: 0 [0], given: 0

Re: Factoring quadratic equation [#permalink] New post 05 Sep 2013, 10:39
Yes, you right, following the rules mentioned to get the second and the third number is imposible by factoring. Thanks a lot for the clue " GMAT would NEVER ask you to factor such an equation"

Thanks again!
Expert Post
1 KUDOS received
Veritas Prep GMAT Instructor
User avatar
Joined: 11 Dec 2012
Posts: 313
Followers: 59

Kudos [?]: 191 [1] , given: 66

Re: Factoring quadratic equation [#permalink] New post 05 Sep 2013, 20:19
1
This post received
KUDOS
Expert's post
Yup some quadratic expressions won't have simple "real number" solutions. The great thing about having no calculator on the GMAT is that the numbers they give will always be solvable fairly quickly by inspection, that is determining what the factors are of C and combining them (+ or -) to form B.

This question reminds me of a question we had in university. What are the roots of x^2 + 2x +10. There's no way to solve this without complex roots, as you can pretty quickly see that no integers (or fractions) will work here. Thankfully, this also means it would never be on the GMAT.

Remember the next time the GMAT frustrates you: everything you can be asked on the exam is known and the math never gets that bad. I know the exam isn't always straight forward but at least it's fair.

Hope this helps!
-Ron
_________________

Ron Awad
Veritas Prep | GMAT Instructor
Save $100 on Veritas Prep GMAT Courses and Admissions Consulting Services
Veritas Prep Reviews

Re: Factoring quadratic equation   [#permalink] 05 Sep 2013, 20:19
    Similar topics Author Replies Last post
Similar
Topics:
3 Experts publish their posts in the topic Factoring quadratic equation bandala 3 04 Sep 2013, 09:49
1 Experts publish their posts in the topic Problem factoring difficult quadratic equation Samwong 3 30 Aug 2013, 10:18
Experts publish their posts in the topic Factoring quadratic equations KarolPL 3 14 Nov 2012, 13:18
3 Experts publish their posts in the topic Factoring quadratic equations jfk 7 02 Apr 2012, 18:06
Quadratic Equation w07 3 16 Jul 2005, 06:48
Display posts from previous: Sort by

Factoring quadratic equation

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.