Question

If A = i+j+2k and B = 2i-j+k, find (A+2B)(2A-3B)​

Answer 1

Answer:

(A+2B)(2A-3B)={(i+ j+2k)+2(2i-j+k)}{2(i+j+2k)-3(2i-j+k)}

=(5i-j+4k)(-4i+5j+k)

=-20-5+4

=-21