Subject: General Aptitude · Chapter: Surds and Indices · Exam: · Marks: · Difficulty:
If abc = 1, then = ? 1 + 1 + c + a − 1 (C.D.S. 2004 287
(a)0
(b)1
(c)1
(d)ab ab
Answer
Answer (as printed): B
Explanation
Given Exp. = + + 1 + a + b− 1 1 + b + c− 1 1 + c + a− 1 1 b− 1 a = −1 + −1 + b + 1 + b − 1c − 1 a + ac + 1 1+ a + b 1 b− 1 a = −1 + −1 + −1 1+ a + b 1+ b + a a + b +1 1 + a + b− 1 = = 1. 1 + a + b− 1 [ abc = 1 ⇒ (bc)–1 = a ⇒ b–1c–1 = a and ac = b–1] 1 1 1 1 1
Explanation as extracted from the printed page; notation may be imperfect.