I3.4 If -2 and $216 c$ are the roots of the equation $p x^{2}+d x=1$, find the value of $d$.
$\begin{array}{l}-2 \text { and } 9 \text { are roots of } p x^{2}+d x-1=0 \\ \text { Product of roots }=-\frac{1}{p}=-2 \times 9 \Rightarrow p=\frac{1}{18} \\ \text { Sum of roots }=-\frac{d}{p}=-2+9 \Rightarrow-18 d=7 \Rightarrow d=-\frac{7}{18}\end{array}$