Which one of the following is true always for any two non-singular matrices A and B of same order ?
AB = BA
(AB)t = AtBt
(A + B)(A - B) = A2 - B2
(AB)- 1 = B- 1A- 1
The vectors of magnitude a, 2a, 3a meet at a point and their directions are along the diagonals of three adjacent faces of a cube. Then, the magnitude of their resultant is
5a
6a
10a
9a
Which one of the following vectors is of magnitude 6 and perpendicular to both ?
D.
Required vector
But its magnitude is not 6.
Therefore correct answer is