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# For Integers A and B, if SQRT(A^3 - A^2 -B) = 7, what is the

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Senior Manager
Joined: 19 May 2004
Posts: 291
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For Integers A and B, if SQRT(A^3 - A^2 -B) = 7, what is the [#permalink]  15 Nov 2004, 12:10
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Question Stats:

0% (00:00) correct 100% (01:23) wrong based on 1 sessions
For Integers A and B, if SQRT(A^3 - A^2 -B) = 7, what is the value of A?

1. A^2 - A = 12
2. B^2 - B = 2
Director
Joined: 07 Nov 2004
Posts: 694
Followers: 4

Kudos [?]: 29 [0], given: 0

I pick C as well.

S(1) gives a = 4 , -3 insufficient
S(2) gives b= 2, -1 insufficient

but using 1 & 2 we can solve for a.
Senior Manager
Joined: 19 Oct 2004
Posts: 318
Location: Missouri, USA
Followers: 1

Kudos [?]: 22 [0], given: 0

Im getting C..

Statement 1-

a^3-a^2-b=49
12a-b=49-------- insuff.

statement 2-

after all the simplification i get a^3-a^2-b^2=47 .... insuff.

combining both,

(b+1)(b-2)=0

b=-1 or 2
substituting for a in statement 1, a= 4 or 17/4. we can leave out the last value, since a= integer.
_________________

Let's get it right!!!!

Manager
Joined: 09 Sep 2004
Posts: 166
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Kudos [?]: 1 [0], given: 0

I do not understand. Could some one explain this in itsy bitsy bits!

Ta very mcuh!
Director
Joined: 31 Aug 2004
Posts: 606
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I would choose B.

Statement 1 is unuseful : A = 4 or -3

Statement 2 : B = 2 or -1

we know from the stem that sqrt(A^3-A^2-B)=7 => A^3-A^2=48 or 51
A being an integer only A=4 matches with 48
Senior Manager
Joined: 19 May 2004
Posts: 291
Followers: 1

Kudos [?]: 8 [0], given: 0

twixt,
You got it

It's B.
I find it a very difficult question.
I wonder, How long did it take you to solve this one ?
Director
Joined: 31 Aug 2004
Posts: 606
Followers: 3

Kudos [?]: 43 [0], given: 0

Keep posting this kind of hard DS Dookie this is good brainstorm material !

By the way where are they from ?

This one took me 12 lines on a scratch paper, 3 minutes I guess. I was suspicious as I had a really similar one during the real test and I always try to be cautious when dealing with integers and well rounded results
Director
Joined: 07 Nov 2004
Posts: 694
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Kudos [?]: 29 [0], given: 0

thanks twixt for the solution and Dookie for posting this problem!
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