CBSE 2023 · Region 3 · Set 1 · Q20 · 1 mark

Assertion (A) : A line through the points ($\displaystyle 4$, $\displaystyle 7$, $\displaystyle 8$) and ($\displaystyle 2$, $\displaystyle 3$, $\displaystyle 4$) is parallel to a line through the points $\displaystyle (-1,-2,1)$ and $\displaystyle (1,2,5)$. Reason $\displaystyle (R)$ : Lines $\displaystyle \overrightarrow{\mathrm{r}}=\overrightarrow{\mathrm{a}_{1}}+\lambda \overrightarrow{\mathrm{b}_{1}}$ and $\displaystyle \overrightarrow{\mathrm{r}}=\overrightarrow{\mathrm{a}_{2}}+\mu \overrightarrow{\mathrm{b}_{2}}$ are parallel if $\displaystyle \overrightarrow{\mathrm{b}_{1}} \cdot \overrightarrow{\mathrm{~b}_{2}}=0$.

CBSE Class 12 Mathematics past-paper question from the 2023board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.