1. The problem statement, all variables and given/known data There is points: P=(1,2,3,4) Q=(4,3,2,1) and line L passes through P and is parallel to A A=(1,1,1,1). X(t) is anypoint on line L. 1. Find the distance between X and Q as a fucntion of t. 2. Find the minimum distance between Q and the line.(which is 2(51/2)) 2. Relevant equations Parametric equations.... distance between two points. 3. The attempt at a solution Im really not sure if my approach is right at all.... i just want to understand where im going wrong. For 1. I tried the parametric equation of the line which is X(t)=P+At to go from X(t) to Q its X(t)-Q=(P-Q)+At=(-3,-1,1,3)+(1,1,1,1)t X(t)-Q=(-3+t,-1+t,1+t,3+t) the distance between X(t) and Q would be d=||(X(t)-Q)|| or d=((X(t)-Q).(X(t)-Q))1/2 For 2. then the distance squared as a function of t would be d2=(X(t)-Q).(X(t)-Q) this gives d2=20+4t2 the derivative is (d2)'=2((d2)'d(2 (d2)'=(2(8t)(20+4t2) (d2)'=320t+64t3 set the derivative to 0 for minimum and i get t=(-320/64)1/2 Its clearly not the right answer of 2(5)1/2 I dont know where im going wrong.