Write the coefficient of $x^{2}$ in each of the following:
$(i)$ $\frac{\pi}{6} x + x^{2} - 1$
$(ii)$ $3x - 5$

(N/A) $(i)$ The given polynomial is $\frac{\pi}{6} x + 1 \cdot x^{2} - 1$. Comparing this with the standard form,the coefficient of $x^{2}$ is $1$.
$(ii)$ The given polynomial $3x - 5$ can be written as $0 \cdot x^{2} + 3x - 5$. Therefore,the coefficient of $x^{2}$ in this polynomial is $0$.