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

It is currently 21 Aug 2014, 16:13

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

Find the value of 'b' if sqrt7 is a root of the equation x^2

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Senior Manager
Senior Manager
User avatar
Joined: 30 Aug 2003
Posts: 330
Location: BACARDIVILLE
Followers: 1

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

GMAT Tests User
Find the value of 'b' if sqrt7 is a root of the equation x^2 [#permalink] New post 30 Jan 2004, 15:20
Find the value of 'b' if sqrt7 is a root of the equation x^2 + ax - 14 = 0 and the equation x^2 + ax + b = 0 has real and equal roots.

7/4
-7/4
49/4
:roll:
none of these
_________________

Pls include reasoning along with all answer posts.
****GMAT Loco****
Este examen me conduce jodiendo loco

Manager
Manager
avatar
Joined: 25 Jan 2004
Posts: 92
Location: China
Followers: 1

Kudos [?]: 2 [0], given: 0

 [#permalink] New post 30 Jan 2004, 15:29
from the second eqn: equal and real roots
a^2 = 4b

from the first eqn, let k be the other root

sqrt(7)+ k = - a
ksqrt(7) = -14

Thus b = (1/4)[sqrt(7) - [14/sqrt(7)]]^2

Last edited by Zhung Gazi on 30 Jan 2004, 16:12, edited 1 time in total.
Senior Manager
Senior Manager
User avatar
Joined: 30 Aug 2003
Posts: 330
Location: BACARDIVILLE
Followers: 1

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

GMAT Tests User
 [#permalink] New post 30 Jan 2004, 15:33
Answer is (A)

Rakesh, we did a similar problem yesterday, but I am having problems with this question. Can u help
_________________

Pls include reasoning along with all answer posts.
****GMAT Loco****
Este examen me conduce jodiendo loco

Manager
Manager
User avatar
Joined: 26 Dec 2003
Posts: 227
Location: India
Followers: 1

Kudos [?]: 2 [0], given: 0

GMAT Tests User
 [#permalink] New post 30 Jan 2004, 15:54
Yeah ur posting such wonderful avathars. We go step by step

from the first eq. let p & q be the roots then we know that p+q= - b/a (the eq is of the form ax^2 + bx +c ), so p+q = -a/1 = -a ( eq is x^2+ax-14) and pq = c/a = -14, we are given that one root is sqrt7 then let p=sqrt7 , we know that pq=-14, so (sqrt7* q) = -14 solve and we get q = -2sqrt7, we also know that p =sqrt7 and p+q = -a, substitute the values of p & q and we get a=sqrt7----------------(1)

from the second eq, we r given that it has real and equal roots so it means b^2- 4ac=0 ( for eq of the form ax^2 +bx +c) so as the given eq is of the form x^2 +ax+b=0 , we get a^2 - 4 * 1 * b=0, so a^2=4b, we know that a=sqrt7 ( from -----(1) above) substitute this value of a in a^2=4b and we get b=7/4.
Senior Manager
Senior Manager
User avatar
Joined: 30 Aug 2003
Posts: 330
Location: BACARDIVILLE
Followers: 1

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

GMAT Tests User
 [#permalink] New post 30 Jan 2004, 16:32
:thanks
_________________

Pls include reasoning along with all answer posts.
****GMAT Loco****
Este examen me conduce jodiendo loco

  [#permalink] 30 Jan 2004, 16:32
    Similar topics Author Replies Last post
Similar
Topics:
Experts publish their posts in the topic Find a possible value of a+b given the equations SravnaTestPrep 1 03 Jan 2013, 03:36
2 Experts publish their posts in the topic If there is exactly one root of the equation x^2 + ax + b carcass 7 03 Mar 2012, 17:14
Experts publish their posts in the topic If there is exactly one root of the equation x^2 + ax + b naaga 8 23 Aug 2011, 22:17
What are the unique values of b and c in the equation 4x^2 + zerotoinfinite2006 2 27 Oct 2010, 11:12
If equation x^2+bx+c=0 have two same roots, b=? (1) c=9 (2) peergmatclub 2 21 Jun 2008, 18:16
Display posts from previous: Sort by

Find the value of 'b' if sqrt7 is a root of the equation x^2

  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®.