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If a < b , is a > 0 ?

(1) \(a^2 < b^2\)..
\(a^2<b^2\) means |a|<|b|..
Let us see what |a|<|b| tells us
There can be two cases when |a|<|b| ..
a) b is positive.... then b>a
b) b is negative...then b<a..
These hold true irrespective of value of a

It is given b>a ... Therefore, we can just say b is positive and nothing about a..
example.. a=2 and b=4, OR a=-2 and b=4..
Insufficient

(2) \(a^2 < ab < b^2\)
\(a^2<ab......ab-a^2>0....a(b-a)>0\)
Now, we know b-a>0 as b>a, therefore a>0...
Since positive*positive>positive
Sufficient

B
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Given a<b i.e a-b<0;

St1:
\(a^2 < b^2\)

\(a^2 - b^2 < 0\) which can be written as (a+b)(a-b) < 0. Because it is given that (a-b) < 0, (a+b) has to be > 0.

Thus a can be positive or negative. Not sufficient.

St2:
Break it down as: 1) \(a^2 < ab\) and 2) \(ab < b^2\) and 3) \(a^2 < b^2\)

1: \(a^2 - ab < 0\) => a(a-b) < 0; Because Q states that a-b < 0, a must be > 0.
2. \(ab - b^2 < 0\) => b(a-b) <0; Thus, b must be > 0.
3. \(a^2 - b^2 < 0\) => Thus a+b must be > 0.

1&2&3: a must be > 0.

St2 is sufficient
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