x<0 Power prep2

This topic has expert replies
Source: — Problem Solving |

Senior | Next Rank: 100 Posts
Posts: 62
Joined: Thu Oct 23, 2008 9:20 am

Re: x<0 Power prep2

by tritrantran » Sun Dec 14, 2008 8:56 pm
Feruza Matyakubova wrote:sos!
plug in numbers.

sqrt (-x*|x|), and x has to be negative

let x = -3

sqrt (-(-3)*|-3|)

sqrt (3*3) = 3

3 = -X

Legendary Member
Posts: 574
Joined: Sun Jun 01, 2008 8:48 am
Location: Bangalore
Thanked: 28 times

by vishubn » Sun Dec 14, 2008 9:32 pm
we know x=-ve

|x| is always + ve

-ve(-x)(x)

root x^2

that is +/- x

we know x<0

remember theere cannot be square root of a neagtive value

so -x is the answer

Vishu
KILL !! DIE !! or BEAT my FEAR !!! de@D END!!

Master | Next Rank: 500 Posts
Posts: 247
Joined: Sun Jul 27, 2008 1:39 am
Thanked: 2 times
GMAT Score:660

by orel » Sun Dec 14, 2008 11:39 pm
I thought i would be just X, because the stem says that x<0, so X is already negative.
- ngative X is positive.

im a bit confused here

Master | Next Rank: 500 Posts
Posts: 247
Joined: Sun Jul 27, 2008 1:39 am
Thanked: 2 times
GMAT Score:660

by orel » Sun Dec 14, 2008 11:58 pm
OA is A

Legendary Member
Posts: 2467
Joined: Thu Aug 28, 2008 6:14 pm
Thanked: 331 times
Followed by:11 members

by cramya » Mon Dec 15, 2008 12:54 am
I thought i would be just X, because the stem says that x<0, so X is already negative.
- ngative X is positive.

im a bit confused here
u r right x is negative. When u evaluate the square root u get a positive number.

So the positive square root is nothing but -x.

Eg: positive square root 3

Like Vishu said x=-3 so if u get +3 as the answer from the square root evaluation is nothing but - (-3) = - (x) [SINCE WE TOOK X AS -3]

Hope this helps!

User avatar
Legendary Member
Posts: 2134
Joined: Mon Oct 20, 2008 11:26 pm
Thanked: 237 times
Followed by:25 members
GMAT Score:730

by logitech » Mon Dec 15, 2008 12:59 am
Feruza Matyakubova,

Good luck at your test. It is time to relax and kick back.

Best,
LGTCH
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"

Master | Next Rank: 500 Posts
Posts: 247
Joined: Sun Jul 27, 2008 1:39 am
Thanked: 2 times
GMAT Score:660

by orel » Mon Dec 15, 2008 1:05 am
Thanks Logitech!
Thank you guys for your explanations!
Feruza