inequality

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by Jay@ManhattanReview » Sun Jun 03, 2018 8:34 pm

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B

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E

Global Stats

vaibhav101 wrote:is modulus a+modulus b> modulus a+b?

1) $$a^2>b^2$$
2) b. modulus a<0
We have to determine whether |a| + |b| > |a + b|?

|a| + |b| > |a + b| is poosible only if a and b are opposite in sign. Let's take two cases.

Case 1: Say a = 2 and b = -1

We have |a| + |b| > |a + b| => |2| + |-1| ? |2 - 1| => 2 + 1 ? 1. We see that 3 > 1. The answer is Yes.

Case 2: Say a = 2 and b = 1

We have |a| + |b| > |a + b| => |2| + |1| ? |2 + 1| => 2 + 1 ? 3. We see that 3 = 3. The answer is No.

Let's see each statement one by one.

(1) a^2 > b^2

Both the cases discussed above are applicable here too. Insufficient.

(2) b.|a| < 0

Since |a| is a positive quantity (irrespective of whether a is positive or negative), and b.|a| is negative, it implies that b is negative.

If a and both are negative, the answer is NO. Say a = b = -1. Then |a| + |b| = |a + b|. The aswer is No.
However, if a is positive and b is negative, the answer is Yes. Say a = 1 and b = -1. Then |a| + |b| > |a + b|. The aswer is Yes.

(1) and (2) together:

Both the cases discussed above are applicable here too. Insufficient.

The correct answer: E

Hope this helps!

-Jay
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