Assertion (A): Lines given by x= py + q, z = ry + s and x= p^′ y + q^′, z = r^′ y + s^′ are perpendicular to each other when pp^′+ rr^′=1. Reason…

Assertion (A) : Lines given by $\displaystyle x=\mathrm{py}+\mathrm{q}, \mathrm{z}=\mathrm{ry}+\mathrm{s}$ and $\displaystyle x=\mathrm{p}^{\prime} \mathrm{y}+\mathrm{q}^{\prime}$, $\displaystyle \mathrm{z}=\mathrm{r}^{\prime} \mathrm{y}+\mathrm{s}^{\prime}$ are perpendicular to each other when $\displaystyle \mathrm{pp}^{\prime}+\mathrm{rr}^{\prime}=1$. Reason (R) : Two lines $\displaystyle \vec{\mathrm{r}}=\vec{a}_{1}+\lambda \vec{b}_{1}$ and $\displaystyle \vec{\mathrm{r}}=\vec{a}_{2}+\mu \vec{b}_{2}$ are perpendicular to each other if $\displaystyle \vec{b}_{1} \cdot \vec{b}_{2}=0$.