If 
and 
then prove that 
and 
are coplanar.
If 
are coplanar then 
= 0
L.H.S = 
- 2( - 8 - 4) + 2(4 + 8) + 4(4 - 16) = 24 + 24 - 48 = 0 = R.H.S
∴L.H.S = R.H.S
Hence proved that the vectors 
Are coplanar.
1
If and then prove that and are coplanar.
If are coplanar then = 0
L.H.S = - 2( - 8 - 4) + 2(4 + 8) + 4(4 - 16) = 24 + 24 - 48 = 0 = R.H.S
∴L.H.S = R.H.S
Hence proved that the vectors
Are coplanar.