Question

69. If A = 3i + 6j, B = xi + k and A.B =12, then x.will be
equal to
(A) 2 (B) 4 (C) 12 (D) 3​

Answer 1

Answer:

x=4

Explanation:

Given, A = 3i + 6j and B = xi + k

A.B= 12

(3i+6j).(xi+k)=12

3xi.i+6xj.i+3i.k+6j.k=12

but, i.i=1, j.i=j.k=0

3x=12

x=4

this is required answer.