Q. 9
Mark the correct alternative in the following:
If 
, then a =
A. 2
B. 3
C. 4
D. none of these
Answer :
a2 – a = 2 + 4 ( nCx = nCy ⇒ n = x + y or x = y )
a2 – a – 6 = 0
a2 – 3a – 2a – 6 = 0
a(a – 3) + 2(a – 3) = 0
(a + 2) (a – 3) = 0
a = -2 or a = 3
But, a = -2 is not possible since it’s negative.
So, a = 3.
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