Lesson: Strange Operators

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If xθy=(x+1)/(y−1) for all y≠1, and aθb=1, then a=

A. b−2
B. b−1
C. b
D. b+1
E. b+2

I did (a+1)/(b-1) = 1
I don't understand what should I do to take out a
Thanks in advance
gmat-admin's picture

Let's take it from (a+1)/(b-1) = 1
Multiply both sides of the equation by (b-1) to get: (a+1) = 1(b-1)
Expand right side: a + 1 = b - 1
Subtract 1 from both sides: a = b - 2

Answer: A

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