What is the coefficient of $x^{3}y$ in $-8x^{3}y{z}^2$?

The coefficient of $x^9$ in the expansion of $1+x\left)\right((1+x^2)$ $(1+x^3)$ $\cdots$ $(1+x^{100})$ is

Factorise:

$3+23z-8z^2$

The positive value of m for which the coefficient of $x^2$ in the expansion od $(1+x{)}^m$ is 6 is