Answer
Parallel
Work Step by Step
$n_1=\lt9,-3,6\gt$ and $n_2=\lt 6,-2,4\gt$
Angle between two vectors$\theta= cos^{-1}|\dfrac{a.b}{|a||b|}|$
$\theta= cos^{-1}|\dfrac{84}{\sqrt {126} \sqrt {56}}|$
$\theta= cos^{-1}|\dfrac{84}{\sqrt {7056}}|$
$\theta =0 ^{\circ}$
Hence, the two planes are parallel.