The coefficient of `a^8b^4c^9d^9` in `(a b c+a b d+a c d d+b c d)^(10)` is `10 !` b. `(10 !)/(8!4!9!9!)` c. `2520` d. none of these
The coefficient of `a^8b^4c^9d^9`
in `(a b c+a b d+a c d d+b c d)^(10)`
is
`10 !`
b. `(10 !)/(8!4!9!9!)`
c. `2520`
d. none of these
A. `10!`
B. `(10!)/(8!4!9!9!)`
C. `2520`
D. none of these
4 views
1 Answers
Correct Answer - C
`a^(10)b^(10)c^(10)d^(10)(1/a+1/b+1/c+1/d)^(10)`
Therefore the required coefficient is equal to the coefficient of
`a^(-2)b^(-6)c^(-1)d^(-1)` in `(1/a+1/b+1/c+1/d)^(10)`, which is given by
`= (10!)/(2!6!1!1!) = (10 xx 9 xx 8 xx 7)/(2) = 2520`
4 views
Answered