Question

Please solve question no-18 answer is option 'c'......Please give step wise solution..

Answer 1

Whenever you have to prove that 2 vectors are perpendicular just find their dot product which is a*b*cosθ where θ=90° and hence the dot product will be equated to 0

In this case the 2 vectors are a+bt and a(when t=0)

Finding their dot product will give you $a^{2}+abt$

By rearranging we get t=$-|a^{2}|/ab$

Hence option b is your answer