Is Sqrt (x-5)^2 = 5 - x : DS Archive
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 19 Jan 2017, 07:24

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Is Sqrt (x-5)^2 = 5 - x

Author Message
Intern
Joined: 04 Sep 2005
Posts: 4
Followers: 0

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

Is Sqrt (x-5)^2 = 5 - x [#permalink]

### Show Tags

22 Sep 2005, 12:41
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

### HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Is Sqrt (x-5)^2 = 5 - x ?

1) -x |x| > 0

2 ) 5 - x > 0

OG explanation starts by saying that Sqrt (y)^2 = |y|. I can't understand that statement. Isn't Sqrt (y)^2 = + or - y ???

I feel i'm missing something here...any help would be appreciated.
Manager
Joined: 06 Aug 2005
Posts: 197
Followers: 3

Kudos [?]: 12 [0], given: 0

### Show Tags

22 Sep 2005, 13:15
No sqrt(x^2) = x
and sqrt ((-x)^2) = x

Exactly how was the expression on the left formatted ?
VP
Joined: 22 Aug 2005
Posts: 1120
Location: CA
Followers: 1

Kudos [?]: 102 [0], given: 0

### Show Tags

22 Sep 2005, 14:38
zag1979 wrote:
I have a problem understanding the solution of this DS problem:

Is Sqrt (x-5)^2 = 5 - x ?

1) -x |x| > 0

2 ) 5 - x > 0

OG explanation starts by saying that Sqrt (y)^2 = |y|. I can't understand that statement. Isn't Sqrt (y)^2 = + or - y ???

I feel i'm missing something here...any help would be appreciated.

is it D.

well to me, what they are saying is:
sqrt(y * y) = y

in this case we omit -y as possible result since we know beforehand number being squared. in other words:
sqrt(4) = +2/-2 but
sqrt(-2 * -2) = -2 or
sqrt(2 * 2) = 2
Director
Joined: 23 Jun 2005
Posts: 847
GMAT 1: 740 Q48 V42
Followers: 5

Kudos [?]: 70 [0], given: 1

### Show Tags

22 Sep 2005, 18:11
I can see that sqrt (x-5)*(x-5) is x-5. But, as duttsit, I think the answer is D.
Intern
Joined: 04 Sep 2005
Posts: 4
Followers: 0

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

### Show Tags

22 Sep 2005, 23:33
OA is D.

The expression on the left is formatted this way:

Sqrt ((x-5)^2)

What the OE basically says is that Sqrt ((x-5)^2) = x - 5 if x - 5 is positive and it is 5 - x if x - 5 is negative.

If I go by the same logic then Sqrt ((-2).(-2)) = 2 and cannot be equal to -2. I don't really see the reason behind that. Why couldn't the root be -2?
Intern
Joined: 18 Sep 2005
Posts: 8
Followers: 0

Kudos [?]: 1 [0], given: 0

### Show Tags

23 Sep 2005, 00:12
zag1979 wrote:
If I go by the same logic then Sqrt ((-2).(-2)) = 2 and cannot be equal to -2. I don't really see the reason behind that. Why couldn't the root be -2?

The official rule is that the sqrt(x^2) = abs(x) for every real number x.

Negatives inside sqrts mean imaginary numbers. Not on the test.

Edit: Hopefully I haven't added to the confusion - it's late & my brain is fried. If you're lost, check out basic imaginary number stuff. IE, sqrt(-1) = i. ... Again, NOT on the test.
Re: OG DS Question   [#permalink] 23 Sep 2005, 00:12
Display posts from previous: Sort by