1. The problem statement, all variables and given/known data Hey guys, I have two separate questions. 1.) I am asked for a unit vector pointing from P = (1,2) to Q = (4,6) In physics, every vector I've ever worked with started at the origin, so these feel weird. I initially thought that it would simply be 3i + 4j, the differences of each coordinate. However, my book gives the answer as (3/5)i + (4/5)j, they divided each number by sqrt(3^2 + 4^2). But why? Why specifically divide by that? If I understand correctly, if you divide both numbers by any one number, the vector will still point the same way because you just make a similar triangle. Why divide by vector length? 2.) Limits and Continuity has been very confusing for me. I am asked to show that f(x,y) does not have a limit as (x,y) -> (0,0), and it says (Hint: use the line y = mx) The function is (x^2 - y^2)/(x^2 + y^2). How do I use y = mx? 2. Relevant equations 3. The attempt at a solution Looking for more of a explanation to help me better understand, not a solution.