Answer
perpendicular
Work Step by Step
$n_1=\lt 5,2,3\gt$ and $n_2=\lt -4,1,6\gt$
Angle between two vectors$\theta= cos^{-1}[\dfrac{a.b}{|a||b|}]$
$\theta= cos^{-1}[\dfrac{-20+2+18}{\sqrt {25+4+9} \sqrt {16+1+36}}]$
$\theta= cos^{-1}[\dfrac{0}{\sqrt {25+4+9} \sqrt {16+1+36}}]$
$=cos^{-1}[0]$
$=90 ^{\circ}$
Hence, the two planes are perpendicular.