If a=i+j+4k and b=i+j+2k Compute the cross product a×b.?

a × b
= (i + j + 4k) × (i + j + 2k)
= (1*2 - 4*1)i + (4*1 - 1*2)j + (1×1 - 1*1)k
= -2i + 2j + 0k

Hint: What formula, or procedure did you see/learn for the cross product?

Write it here and then we will proceed.

If a = i + j + 4k and b = i + j + 2k 
the cross product a × b: 
(i + j + 4k)(i + j + 2k) = j^2 + 6 j k + 2 i (j + 3 k) + 8 k^2 - 1