inequality and variable

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

Redeem

This topic has expert replies

Post new topic Post Reply

Previous Topic Next Topic

Gurpinder: Legendary Member; Posts: 659; Joined: Mon Dec 14, 2009 8:12 am; Thanked: 32 times; Followed by:3 members

inequality and variable

by Gurpinder » Fri Sep 03, 2010 10:38 am

X^2 < 4, what are the possible values for x?

shouldnt x = -2

because x could be 2,-2 but only -2 is les than 2 as in the question?

2<2
-2<2 <<< this should be the answer right?

"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.

Quote

Source: Beat The GMAT — Problem Solving | Fri Sep 03, 2010 10:38 am

debmalya_dutta: Master | Next Rank: 500 Posts; Posts: 385; Joined: Sun Jul 12, 2009 10:16 pm; Thanked: 29 times; Followed by:2 members; GMAT Score:710

by debmalya_dutta » Fri Sep 03, 2010 11:00 am

Gurpinder wrote:X^2 < 4, what are the possible values for x?

shouldnt x = -2

because x could be 2,-2 but only -2 is les than 2 as in the question?

2<2
-2<2 <<< this should be the answer right?

X^2 < 4
X^2 - 2 ^2 < 0
(X+2)(X-2) < 0

so -2< X < +2 .. All values between -2(excluding) and +2 (excluding)

@Deb

Quote

Gurpinder: Legendary Member; Posts: 659; Joined: Mon Dec 14, 2009 8:12 am; Thanked: 32 times; Followed by:3 members

by Gurpinder » Fri Sep 03, 2010 11:02 am

debmalya_dutta wrote:
Gurpinder wrote:X^2 < 4, what are the possible values for x?

shouldnt x = -2

because x could be 2,-2 but only -2 is les than 2 as in the question?

2<2
-2<2 <<< this should be the answer right?
X^2 < 4
X^2 - 2 ^2 < 0
(X+2)(X-2) < 0

so -2< X < +2 .. All values between -2(excluding) and +2 (excluding)

AHH...thx

i was just taking the sq. root of both sides. is that wrong?

"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.

Quote

debmalya_dutta: Master | Next Rank: 500 Posts; Posts: 385; Joined: Sun Jul 12, 2009 10:16 pm; Thanked: 29 times; Followed by:2 members; GMAT Score:710

by debmalya_dutta » Fri Sep 03, 2010 11:16 am

Gurpinder wrote:
debmalya_dutta wrote:
Gurpinder wrote:X^2 < 4, what are the possible values for x?

shouldnt x = -2

because x could be 2,-2 but only -2 is les than 2 as in the question?

2<2
-2<2 <<< this should be the answer right?
X^2 < 4
X^2 - 2 ^2 < 0
(X+2)(X-2) < 0

so -2< X < +2 .. All values between -2(excluding) and +2 (excluding)
AHH...thx

i was just taking the sq. root of both sides. is that wrong?

taking square root also works but then you should build the inequality as
|X|< 2
Its just that its a cleaner way to approach (ofcourse per me) ..You are free to disagree