If $n$ is even positive integer, then the condition that the greatest term in the expansion of ${(1 + x)^n}$ may have the greatest coefficient also, is
$\frac{n}{{n + 2}} < x < \frac{{n + 2}}{n}$
$\frac{{n + 1}}{n} < x < \frac{n}{{n + 1}}$
$\frac{n}{{n + 4}} < x < \frac{{n + 4}}{4}$
None of these
The coefficient of ${x^{ - 7}}$ in the expansion of ${\left( {ax - \frac{1}{{b{x^2}}}} \right)^{11}}$ will be
The ratio of the coefficient of terms ${x^{n - r}}{a^r}$and ${x^r}{a^{n - r}}$ in the binomial expansion of ${(x + a)^n}$ will be
The coefficient of $t^4$ in the expansion of ${\left( {\frac{{1 - {t^6}}}{{1 - t}}} \right)^3}$ is
The coefficient of $x ^7$ in $\left(1-x+2 x^3\right)^{10}$ is $........$.
Coefficient of $x$ in the expansion of ${\left( {{x^2} + \frac{a}{x}} \right)^5}$ is