The correct option is
B 0Given →a,→b,→c are coplanar if there exists three scalars x,y,z such that
x→a+y→b+z→c=0, .........(1)for (x,y,z)≠0
Taking the dot product of →a with eqn(1) we get
x→a.→a+y→b.→a+z→c.→a=0.→a,
x→a.→a+y→b.→a+z→c.→a=0 .........(2)
Taking the dot product of →b with eqn(1) we get
x→a.→b+y→b.→b+z→c.→b=0.→b,
x→a.→b+y→b.→b+z→c.→b=0 .........(3)
Taking the dot product of →c with eqn(1) we get
x→a.→c+y→b.→c+z→c.→c=0.→c,
x→a.→c+y→b.→c+z→c.→c=0 .........(4)
From (2),(3) and (4) we have a systems of linear homogeneous equations,so the equations have non-trivial solution for x,y and z
∴Δ=0
⇒∣∣
∣
∣∣→a→b→c→a.→a→a.→b→a.→c→a.→b→b.→b→c.→b∣∣
∣
∣∣=0