OG 11 #98

This topic has expert replies
Senior | Next Rank: 100 Posts
Posts: 95
Joined: Wed Feb 09, 2011 6:42 am
Thanked: 1 times
Followed by:1 members

OG 11 #98

by singalong » Tue Aug 09, 2011 1:39 am
If x(2x+1)=0 and (x+1/2)(2x-3)=0 then x=

A) -3
B) -1/2
C) 0
D) 1/2
E) 3/2

Answer is 0 or -1/2?

As a linear equation x(2x+1) can give both 0 and -1/2 right?

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pm
Location: Milpitas, CA
Thanked: 1854 times
Followed by:523 members
GMAT Score:770

by Anurag@Gurome » Tue Aug 09, 2011 1:57 am
singalong wrote:If x(2x+1)=0 and (x+1/2)(2x-3)=0 then x=
From x(2x + 1) = 0, we have either x = 0 or x = -1/2

For, x = 0, (x + 1/2)(2x - 3) = -3/2 ---> Doesn't satisfy equation 2
for x = -1/2, (x + 1/2)(2x - 3) = 0 ---> Satisfies equation 2

Hence, x = -1/2

The correct answer is B
As a linear equation x(2x+1) can give both 0 and -1/2 right?
x(2x + 1) = 0 is not a linear equation, it's a quadratic equation.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/

User avatar
Senior | Next Rank: 100 Posts
Posts: 54
Joined: Sun Nov 29, 2009 7:11 pm
Location: Bangalore
Thanked: 4 times

by abhisays » Tue Aug 09, 2011 2:04 am
x should be -1/2 as it satisfies both the quadratic equations.

Hence answer should be B

Senior | Next Rank: 100 Posts
Posts: 95
Joined: Wed Feb 09, 2011 6:42 am
Thanked: 1 times
Followed by:1 members

by singalong » Sun Oct 30, 2011 5:53 am
thanks

Senior | Next Rank: 100 Posts
Posts: 99
Joined: Sun Mar 13, 2011 12:42 pm

by factor26 » Sun Oct 30, 2011 3:43 pm
singalong ... the best way to solve this question is to plug the answer choices into the question to see which answer choice satisfies both equations: -1/2 satisfies both equations IMO B is the way to go here

Legendary Member
Posts: 2789
Joined: Tue Jul 26, 2011 12:19 am
Location: Chennai, India
Thanked: 206 times
Followed by:43 members
GMAT Score:640

by GmatKiss » Sun Oct 30, 2011 10:38 pm
B: -1/2