Write the coefficient of $x^{2}$ in each of the following:

$(i)$ $\frac{\pi}{6} x+x^{2}-1$

$(ii)$ $3 x-5$

Evaluate the following using suitable identities

$(105)^{3}$

The following expressions are polynomials? Justify your answer:

$\frac{1}{5 x^{-2}}+5 x+7$

Find $p(0), p(1), p(-2)$ for the following polynomials:

$p(x)=10 x-4 x^{2}-3$

If $x+5$ is a factor of $x^{3}+13 x^{2}+a x+35$ find the value of $a$.