if the term independent of x in the expansion of (ax-1/x^2)^6 is 240,find a

Asked by  | 8th Nov, 2012, 12:23: PM

Expert Answer:

In case of binomial expansion of (a+b)n, it is written as
nC0an+nC1an-1b+......+nCnbn
So, for the given expression, the term 6C4 will have axand 1/x4. So
it will be independent of x.
So, 6C4a4=240
Or,
 
a4  =6! / 4!2!240
a4  = 15/240
a4  = 1/16
 
So, a = 1/2

Answered by  | 8th Nov, 2012, 03:55: PM

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