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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 theseA. `10!`B. `(10!)/(8!4!9!9!)`C. `2520`D. none of these |
Answer» 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` |
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