Write the coefficient of x7y2 in the expansion of (x + 2y)9
To find: the coefficient of x7y2 in the expansion of (x + 2y)9
Formula Used:
A general term, Tr+1 of binomial expansionis given by,
Tr+1 nCr xn-r yr where
nCr
Now, finding the general term of the expression, (x + 2y)9, we get
Tr+19Cr
The value of r for which coefficient of x7y2 is defined
r=2
Hence, the coefficient of x7y2 in the expansion of (x + 2y)9 is given by:
T39C3
T39C3
T3
T3
T3=336
Thus, the coefficient of x7y2 in the expansion of (x + 2y)9 is 336