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# What is the value of a + b ?

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Math Expert
Joined: 02 Sep 2009
Posts: 41873

Kudos [?]: 128564 [1], given: 12180

What is the value of a + b ? [#permalink]

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03 Sep 2017, 06:26
1
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63% (01:31) correct 38% (00:16) wrong based on 28 sessions

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What is the value of a + b ?

(1) $$a^2b + ab^2 = 9$$

(2) $$a^2 – b^2 = 5$$
[Reveal] Spoiler: OA

_________________

Kudos [?]: 128564 [1], given: 12180

Senior Manager
Joined: 15 Jan 2017
Posts: 281

Kudos [?]: 21 [0], given: 618

Re: What is the value of a + b ? [#permalink]

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06 Sep 2017, 13:25
B ...
based on st 1: ab(a+b) = 9 ; but a + b =?
st 2: (a+b)(a-B) = 5 --> (3+2)(3-2) = 5

Kudos [?]: 21 [0], given: 618

Intern
Joined: 04 Nov 2015
Posts: 36

Kudos [?]: 2 [0], given: 2

Re: What is the value of a + b ? [#permalink]

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06 Sep 2017, 14:40
B ...
based on st 1: ab(a+b) = 9 ; but a + b =?
st 2: (a+b)(a-B) = 5 --> (3+2)(3-2) = 5

B can't be the answer as a = -3 and b =-2 also yields a^2 - b^2 = 5 .So in this case a+b = -5 while if a = 3 and b =2, a+b = 5.
I suppose the answer has to be E.
Awaiting OA.

Kudos [?]: 2 [0], given: 2

Math Forum Moderator
Joined: 02 Aug 2009
Posts: 4967

Kudos [?]: 5450 [1], given: 112

Re: What is the value of a + b ? [#permalink]

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06 Sep 2017, 16:32
1
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Expert's post
Bunuel wrote:
What is the value of a + b ?

(1) $$a^2b + ab^2 = 9$$

(2) $$a^2 – b^2 = 5$$

hi..

lets see the statements..

(1) $$a^2b + ab^2 = 9$$
$$ab(a+b)=9$$
Various combinations possible..
ab=1, a+b=9
ab=3, a+b=3..
there are no restrictions for a and b as integers, so they can take any value
ab=1/9, a+b=81
and so on
insuff

(2) $$a^2 – b^2 = 5$$
(a-b)(a+b)=5..
again possiblities
a-b=1, a+b=5
a-b=5, a+b=1
there are no restrictions for a and b as integers, so they can take any value
a-b=1/5, a+b=25
insuff

combined..
all values can be possible as no restrictions
insuff

E
_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

Kudos [?]: 5450 [1], given: 112

Re: What is the value of a + b ?   [#permalink] 06 Sep 2017, 16:32
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# What is the value of a + b ?

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