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Is a=b?

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Is a=b? [#permalink]

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New post Updated on: 24 Feb 2017, 08:01
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E

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Is a=b?

1) \(a^2=b^2\)
2) \(a=2\)

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Originally posted by MathRevolution on 24 Feb 2017, 02:15.
Last edited by Bunuel on 24 Feb 2017, 08:01, edited 1 time in total.
Edited the OA.
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Re: Is a=b? [#permalink]

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New post 24 Feb 2017, 03:48
(1) a^2 = b^2;
Suppose, a = 2, and b = 2, Therefore, a = b;

Again, suppose a= 2 and b = -2; In this case also a^2 = b^2 is true, but a ≠ b; Hence, Insufficient.

(2) a = 2; Insufficient;

(1) And (2) together, Insufficient;

Answer E.
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Re: Is a=b? [#permalink]

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New post 24 Feb 2017, 07:45
MathRevolution wrote:
Is a=b?

1) \(a^2=b^2\)
2) \(a=2\)


Hi Bunuel

Can throw some light on this question

Seems like ans is E. Can you validate.
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Re: Is a=b? [#permalink]

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New post 24 Feb 2017, 07:50
MathRevolution wrote:
Is a=b?

1) \(a^2=b^2\)
2) \(a=2\)


In statement 1, If a^2 = b^2, then b can be equal to a or b can be equal to -a because a^2 is also equal to (-a)^2. Hence insufficient
In statement 2, a = 2, but there is no information of b. Hence, insufficient

By combining, if a = 2, then a^2 is 4. But b can be 2 or -2 because 2^2 = 4 and (-2)^2 is also 4.

Hence, together also insufficient.

Thanks,
Anant Saraogi
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Re: Is a=b? [#permalink]

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New post 24 Feb 2017, 07:53
Top Contributor
NandishSS wrote:
MathRevolution wrote:
Is a=b?

1) \(a^2=b^2\)
2) \(a=2\)


Hi Bunuel

Can throw some light on this question

Seems like ans is E. Can you validate.


You're right; the correct answer is E

Statements 1 and 2 combined
Case a: a = 2 and b = 2, in which case a EQUALS b
Case b: a = 2 and b = -2, in which case a DOES NOT EQUAL b
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT

Cheers,
Brent
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Re: Is a=b? [#permalink]

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New post 24 Feb 2017, 18:34
GMATPrepNow wrote:
NandishSS wrote:
MathRevolution wrote:
Is a=b?

1) \(a^2=b^2\)
2) \(a=2\)


Hi Bunuel

Can throw some light on this question

Seems like ans is E. Can you validate.


You're right; the correct answer is E

Statements 1 and 2 combined
Case a: a = 2 and b = 2, in which case a EQUALS b
Case b: a = 2 and b = -2, in which case a DOES NOT EQUAL b
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT

Cheers,
Brent

Thank you Brent :-)

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Re: Is a=b? [#permalink]

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New post 26 Feb 2017, 21:32
==> In the original condition, there are 2 variables (a,b) and in order to match the number of variables to the number of equations, there must be 2 equations. Since there is 1 for con 1) and 1 for con 2), C is most likely to be the answer. By solving con 1) and con 2), from a=2, you get \(b^2=2^2=4\), then b=±2. Thus, (a,b)=(2,2) yes but (a,b)=(2,-2) no, hence it is not sufficient.

The answer is E.
Answer: E
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Re: Is a=b?   [#permalink] 26 Feb 2017, 21:32
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