exponent and root

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deepoe: Master | Next Rank: 500 Posts; Posts: 151; Joined: Wed Feb 11, 2009 2:45 am; Thanked: 3 times

by deepoe » Mon Mar 09, 2009 4:58 am

If x =4 , then -2^2 radical X + 2 =

A. - 14
B. -8
C. -2
D. 0
E. 18

I had chosen E, but it is A :S

-2^2 x 2 = -2^4 +2 = -2 x -2 x -2 x -2 + 2 = 16 + 2 = 18 ?

How can -2^4 be -14 ?

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Source: Beat The GMAT — Problem Solving | Mon Mar 09, 2009 4:58 am

DanaJ: Site Admin; Posts: 2567; Joined: Thu Jan 01, 2009 10:05 amFollowed by: 550 members; Thanked: 712 times; GMAT Score:770

by DanaJ » Mon Mar 09, 2009 5:04 am

-2^[2 + sqrt(4)] = -2^4 = -16.
Now, you're looking for -16 + 2 = -14.
The thing that might have confused you is that the minus sign:
a. since the minus sign is in fron of 2, then you get that -2^4 = -(2^4) = -16
b. had the minus sign been placed like so: (-2)^4 - then indeed you get that (-2)^4 = 16.

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devesh99: Junior | Next Rank: 30 Posts; Posts: 14; Joined: Wed Feb 18, 2009 4:56 pm; Thanked: 1 times

by devesh99 » Mon Mar 09, 2009 5:06 pm

What is radical in this question??? can some one explain

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devesh99: Junior | Next Rank: 30 Posts; Posts: 14; Joined: Wed Feb 18, 2009 4:56 pm; Thanked: 1 times

by devesh99 » Mon Mar 09, 2009 5:07 pm

What is radical in this question??? can some one explain

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DanaJ: Site Admin; Posts: 2567; Joined: Thu Jan 01, 2009 10:05 amFollowed by: 550 members; Thanked: 712 times; GMAT Score:770

by DanaJ » Tue Mar 10, 2009 4:34 am

I attached a photo. Hope it clears things out...

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