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

Redeem

help- solve this 700-800 exponent question FAST (<2min)?

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 47
Joined: Sun Feb 05, 2012 7:56 pm
Followed by:3 members

help- solve this 700-800 exponent question FAST (<2min)?

by queenisabella » Sun Feb 19, 2012 12:04 pm
This ended up taking way too long for me to solve so I ended up guessing. Please share any tips and tricks and shortcuts to solve this.

Each of the following equations has at least one solution EXCEPT

A) -2^n = (-2)^-n

B) 2^-n = (-2)^n

C) 2^n = (-2)^-n

D) (-2)^n = -2^n

E) (-2)^-n = -2^-n
Top
Source: — Problem Solving |
User avatar
Master | Next Rank: 500 Posts
Posts: 425
Joined: Wed Dec 08, 2010 9:00 am
Thanked: 56 times
Followed by:7 members
GMAT Score:690

by LalaB » Sun Feb 19, 2012 12:17 pm
the answ is A,since A has no solution


-2^n = (-2)^-n
please pay attention to the fact, that -2^n means -1* 2^n

so, ur left side is always negative.
2^n can be equal to (-2)^-n ,if n=0 but even then u will have -1=1
so, A has no solution
Happy are those who dream dreams and are ready to pay the price to make them come true.(c)

In order to succeed, your desire for success should be greater than your fear of failure.(c)
Top
Legendary Member
Posts: 1084
Joined: Fri Apr 15, 2011 2:33 pm
Thanked: 158 times
Followed by:21 members

by pemdas » Sun Feb 19, 2012 12:19 pm
supply 0 and 1
A) -2^0 = (-2)^-0
A) -2^1 = (-2)^-1

IOM a
queenisabella wrote:This ended up taking way too long for me to solve so I ended up guessing. Please share any tips and tricks and shortcuts to solve this.

Each of the following equations has at least one solution EXCEPT

A) -2^n = (-2)^-n

B) 2^-n = (-2)^n

C) 2^n = (-2)^-n

D) (-2)^n = -2^n

E) (-2)^-n = -2^-n
Success doesn't come overnight!
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 425
Joined: Wed Dec 08, 2010 9:00 am
Thanked: 56 times
Followed by:7 members
GMAT Score:690

by LalaB » Sun Feb 19, 2012 12:20 pm
pemdas, do u mean that A has 2 answers? I have doubts about that. I think A has no solution at all
Happy are those who dream dreams and are ready to pay the price to make them come true.(c)

In order to succeed, your desire for success should be greater than your fear of failure.(c)
Top
Legendary Member
Posts: 1084
Joined: Fri Apr 15, 2011 2:33 pm
Thanked: 158 times
Followed by:21 members

by pemdas » Sun Feb 19, 2012 12:23 pm
LalaB wrote:pemdas, do u mean that A has 2 answers? I have doubts about that. I think A has no solution at all
i show proportions on LHS and RHS. The sign of equality should be changed from "=" to "!=" for more correctness.
Success doesn't come overnight!
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 425
Joined: Wed Dec 08, 2010 9:00 am
Thanked: 56 times
Followed by:7 members
GMAT Score:690

by LalaB » Sun Feb 19, 2012 12:28 pm
@queenisabella,

as for <2 min, in order to save ur time, gmat writers posted the right answer first. in ur fist attempt (answ choice A) u will get the right answer, and will save ur precious time
Happy are those who dream dreams and are ready to pay the price to make them come true.(c)

In order to succeed, your desire for success should be greater than your fear of failure.(c)
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 406
Joined: Mon Jan 25, 2010 11:36 am
Location: Syracuse, NY
Thanked: 23 times
Followed by:4 members
GMAT Score:740

by tomada » Sun Feb 19, 2012 2:46 pm
Keep in mind that, on the actual test, the correct answer could be the 5th choice.
I'm really old, but I'll never be too old to become more educated.
Top
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pm
Location: New York, NY
Thanked: 13060 times
Followed by:1906 members
GMAT Score:790

by GMATGuruNY » Sun Feb 19, 2012 6:03 pm
I posted a solution here:

https://www.beatthegmat.com/mgcat-700-800q-t81682.html
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top
Post new topic Post Reply
• Page 1 of 1