Target Test Prep 20% Off Flash Sale is on! Code: FLASH20

Redeem
Target Test Prep
5-Day Free Trial
5-day free, full-access trial TTP

Available with Beat the GMAT members only code

MORE DETAILS
Target Test Prep
Magoosh
Magoosh
Study with Magoosh GMAT prep

Available with Beat the GMAT members only code

MORE DETAILS
Magoosh

Roots

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 145
Joined: Mon Feb 16, 2009 8:41 am
Thanked: 2 times
Followed by:2 members

Roots

by anshulseth » Tue May 12, 2009 10:06 am
What is the value of x^2 – 1 ?

1. The value of x^2 – 5x is –6.
2. The value of (x^2-1)/(x+1) is 1.

Regular DS options.

Explain the working plz. Don't just guess.
Asset
Top
Master | Next Rank: 500 Posts
Posts: 199
Joined: Mon Apr 06, 2009 4:15 am
Location: India
Thanked: 13 times

by gauravgundal » Tue May 12, 2009 10:19 am
I would go for C

STM -1

x^2 -5x=-6
x^2 -5x+6=0
x=3 and x=2
Insufficient

STM-2
x^2 -1=x+1
x^2 -x-2=0
x=2 and x =-1
Insufficient

Combining both i can say x=2
x^2-1=3

Please let me know if i am wrong.
THANKS
Top
Junior | Next Rank: 30 Posts
Posts: 21
Joined: Wed Apr 01, 2009 1:04 pm
Location: Toronto, Canada
Thanked: 1 times
GMAT Score:710

by HumbleMe » Tue May 12, 2009 10:22 am
1. x^2-5x = 6 -> x=2 or x=3 -> x^2-1 = 3 or 8

2. x^2-1/x+1 = (x-1)(x+1)/(x+1) = x-1 = 1 -> x = 2

Only 2 is sufficient... Hence B
Top
Master | Next Rank: 500 Posts
Posts: 199
Joined: Mon Apr 06, 2009 4:15 am
Location: India
Thanked: 13 times

by gauravgundal » Tue May 12, 2009 10:28 am
My Mistake
humble u are right
Top
Master | Next Rank: 500 Posts
Posts: 145
Joined: Mon Feb 16, 2009 8:41 am
Thanked: 2 times
Followed by:2 members

by anshulseth » Tue May 12, 2009 6:52 pm
@HumbleMe

My question to you is:
Do you know if X is not equal to -1.
Then, how can u cancel X+1 in the 2) option.
Asset
Top
Master | Next Rank: 500 Posts
Posts: 371
Joined: Fri Mar 06, 2009 2:48 am
Thanked: 27 times
GMAT Score:740

by 2010gmat » Tue May 12, 2009 11:30 pm
if x = -1 then (x^2-1)/(x+1) = 1 is not possible....
Top
Master | Next Rank: 500 Posts
Posts: 145
Joined: Mon Feb 16, 2009 8:41 am
Thanked: 2 times
Followed by:2 members

by anshulseth » Tue May 12, 2009 11:47 pm
Got it.
Thanks 2010gmat
Asset
Top
Post new topic Post Reply
• Page 1 of 1