Question:

Image of $P(1,2,3)$ in plane $2x-y+z=9$ is $Q$. $R=(6,10,7)$. Then square of area of $\triangle PQR$ is _______

Step-by-Step Solution

Key Concept: Find $Q$ via reflection formula. Then compute area $=\frac{1}{2}|\overrightarrow{PQ}\times\overrightarrow{PR}|$.

(Area)$^2=594$.

Correct Answer: 594