If 0ab, which of the following CANNOT be true?

Question

If 0ab , which of the following CANNOT be true? A. \frac{(3b+5)}{(1−a)}>8 B. \frac{(a−1)}{(3b+5)}<8 C. \frac{(3b+5)}{(a−1)}<8 D. \frac{(3b+5)}{(a−1)}>8 E. \frac{(1−a)}{(3b+5)}>8

ThatDudeKnows · Answer

If b is positive and ab is negative, that means a must be negative. A. \frac{+}{+}>8 B. \frac{-}{+}<8 C. \frac{+}{-}<8 D. \frac{+}{-}>8 Wait, \frac{+}{-} is negative, so it can't be greater than 8. E. \frac{+}{+}>8 Answer choice D.

chetan2u · Answer

b>0 and ab<0 means a<0. Logical approach A and C are same. Both sides multiplied by - sign and inequality inverted. So eliminate as we cannot have two wrong answers. Similarly for B and E. only D left. Number properties 8 has got nothing to do with question as a and b can take any negative and positive values respectively. So, we are looking for >0 or <0. We are looking at three terms 3b+5, 1-a and a-1. 3b+5 will always be positive 1-a will also be positive as a<0 a-1 will always be negative. A. \frac{(3b+5)}{(1−a)}>8……..\frac{+}{+}>8>0 ….yes B. \frac{(a−1)}{(3b+5)}<8 ……..\frac{-}{+}<8 …..yes C. \frac{(3b+5)}{(a−1)}<8… ……..\frac{+}{-}<8 ….yes D. \frac{(3b+5)}{(a−1)}>8…. ……..\frac{+}{-}>8 ….NO E. \frac{(1−a)}{(3b+5)}>8… ……..\frac{+}{+}>8>0 …yes D

If 0<b, and 0>ab, which of the following CANNOT be true?

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