Q. 1 3.6( 70 Votes )

Find the coefficient of

x5 in (x + 3)8

Answer :

The general term Tr+1 in the binomial expansion is given by Tr+1 = nCr an-r br

Here x5 is the Tr+1 term so

a= x, b = 3 and n =8

Tr+1 = 8Cr x8-r 3r……………1

For finding out x5

We equate x5= x8-r

r= 3

Putting value of r in 1 we get

T3+1 = 8C3 x8-3 33

= 1512 x5

Hence the coefficient of x5= 1512

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