1. With respect to origin O, point A has position vector 30i - 3j - 5k. The line L passes through O and is parallel to the vector 4i - 5j -3k. The point B on L is such that AB is perpendicular to L. Find the length of AB. Find the position vector of B. 3. The attempt at a solution Ok this is what i did. Let L=y(4i -5j -3k) Let b=x(4i -5j -3k) Hence AB = [(4x-30)i (-5x+3)j (-3x+5)k] Heres where i got quite stuck Since AB is perpendicular to L. I tried AB.L=0 But i'm not very sure how do i solve this since there are 2 unknowns. Ahh! Please help me out here! Thanks!