Q. 25.0( 3 Votes )
If the coefficients of x2 and x3 in the expansion of (3 + px)9 are the same then prove that 
.
Answer :
To prove: that. If the coefficients of x2 and x3 in the expansion of (3 + px)9 are the same then 
.
Formula Used:
General term, Tr+1 of binomial expansion
is given by,
Tr+1
nCr xn-r yr where
nCr
Now, finding the general term of the expression, (3 + px)9 , we get
Tr+1
9Cr
For finding the term which has 
in it, is given by
r=2
Thus, the coefficients of x2 are given by,
T3
9C2
T3
9C2
For finding the term which has 
in it, is given by
r=3
Thus, the coefficients of x3 are given by,
T3
9C3
T3
9C3
As the coefficients of x2 and x3 in the expansion of (3 + px)9 are the same.
9C3
9C2
9C3
9C2
Thus, the value of p for which coefficients of x2 and x3 in the expansion of (3 + px)9 are the same is 
Rate this question :
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Show that the coefficient of x4 in the expansion of 
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is -330.
Show that the term independent of x in the expansion of 
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