1 The plane \(\Pi\) passes through the points with coordinates \(( 1,6,2 ) , ( 5,2,1 )\) and \(( 1,0 , - 2 )\).
- Find a vector equation of \(\Pi\) in the form \(\mathbf { r } = \mathbf { a } + \lambda \mathbf { b } + \mu \mathbf { c }\).
- Find a cartesian equation of \(\Pi\).
\(2 G\) consists of the set \(\{ 1,3,5,7 \}\) with the operation of multiplication modulo 8 .