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7.Binomial Theorem
easy
The term independent of $x$ in the expansion of ${\left( {{x^2} - \frac{1}{x}} \right)^9}$ is
A
$1$
B
$-1$
C
$-48$
D
None of these
Solution
(d) $(9 -r) (2) + r (-1) = 0$
==> $18 -2r -r = 0$ ==> $r = 6$
Thus term independent of $x$ is $^9{C_6}{(1)^3}{( – 1)^6} = 84.$
Standard 11
Mathematics