BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

equations

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Legendary Member
Posts: 659
Joined: Mon Dec 14, 2009 8:12 am
Thanked: 32 times
Followed by:3 members

equations

by Gurpinder » Fri Sep 03, 2010 10:01 am
what is the value of a(b)^2 ?

(1) a = b-1
(2) a=(b^2) - 1

thx
"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.
Top
Source: — Data Sufficiency |
Senior | Next Rank: 100 Posts
Posts: 52
Joined: Thu Feb 25, 2010 9:08 am
Thanked: 5 times

by akdayal » Fri Sep 03, 2010 11:05 am
statement 1.
a = b -1 ==> a[(a+1)^2] = (b -1)(b)^2
It depends on value of a or b so, st1 is not sufficient.

Statement2.
a = (b^2) - 1 ==> a(b)^2 = a(a +1) = ((b)^2 + 1)((b)^2)
Again it depends on value of a or b so, st2 is also not sufficient.

consider both together.
a = b - 1 --- (1)
a = b^2 -1 = (b -1)(b + 1) ----(2)
from eq (1) and (2)
(b-1)b = 0 ==> b = 0 or 1 .
if b = 0 then a = -1 ==> a(b)^2 = 0
if b = 1 then a = 0 ==> a(b)^2 = 0
Hence together are sufficient.
Ans should be C
Top
Post new topic Post Reply
• Page 1 of 1