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Is |a^2-b^2|<10?

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Is |a^2-b^2|<10? [#permalink]

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New post 14 Jul 2016, 21:34
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A
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C
D
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Is |a^2-b^2|<10?
1) |a-b|<5
2) |a+b|<2

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[Reveal] Spoiler: OA

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Re: Is |a^2-b^2|<10? [#permalink]

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New post 14 Jul 2016, 22:45
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My Answer is C)

Below is my explanation, Please feel free to correct me, if wrong.
given |(a+b)(a-b)| < 10 --> A

a) |a-b| < 5
Let a = 10 , b = 7 : Above eq A is not satisfied
a = 3 , b = -2 : Above eq A is satisfied
Therefore, Not Suff.

b) |a+b| <2
If a = 1, b = 1/2 : Eq A is satisfied
a = 10 , b = -9 : Eq A is not satisfied.
Therefore, Not Suff.

a + b => Sufficient. Hence, C

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Re: Is |a^2-b^2|<10? [#permalink]

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New post 18 Jul 2016, 09:16
Since there are 2 variables in the original condition, the correct answer is C.

- Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.
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Re: Is |a^2-b^2|<10? [#permalink]

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New post 19 Jul 2016, 01:55
Could I seperate the equation |(a+b)(a-b)|<10 as |a+b|*|a-b|<10?

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Is |a^2-b^2|<10? [#permalink]

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New post 19 Jul 2016, 03:44
tinalongmao wrote:
Could I seperate the equation |(a+b)(a-b)|<10 as |a+b|*|a-b|<10?


Yes, you could.

Remember, Product and Division in absolute values could be separated.

I mean if we have |a/b|, we can write it as |a|/|b|

or |a*b|=|a|*|b|

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Re: Is |a^2-b^2|<10? [#permalink]

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New post 11 Aug 2017, 21:32
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Re: Is |a^2-b^2|<10?   [#permalink] 11 Aug 2017, 21:32
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