Question

If the vectors a=ai+j-2k and b=ai-2j+k are perpendicular to each other then the positive value of a is

Answer 1

Answer:

condition for vectors to be perpendicular :

• a1a2+b1b2+c1/c2 =0
• a^2-2-2=0
• a^2=4
• a=+ or - 2