1. The problem statement, all variables and given/known data Let A=(2,3,-1) and B=(4,-5,7). Find the midpoint of A and B. Find the point Q on the line through A and B such that B lies between A and Q and BQ is three times as long as AB 2. Relevant equations 3. The attempt at a solution So to find the midpoint of A and B. MA+B=(A+B)/2 RHS= (6,-2,6)/2 MA+B=(3,-1,3) Next I said that the the midpoint of Q and A is 3 × (MA+B) Hence MQ+A= (9,-3,9) So now we have the midpoint and one endpoint of the line QA. so Q+A=2(MQ+A) so RHS= (18,-6,18) Hence Q+2=18 Q+3=-6 Q-1=18 so Q=(16,-9,19) But this was wrong I don't see why?