1) given OP = (4, -2, 1) and OQ = (2, 4, 4) Find PQ.

I think I got this right, I got PQ = (6, 2, 5) with magnitude (65)^0.5 ??

2) given OP = (7, -2, 3) and PQ = (0, 3, -4), find OQ

I got OQ = (7, 5, -7)

3) point P = (1, 2, 3), find points R and Q such that a = PQ and b=PR and obtain the vector QR

I would appreciate someones input/help on this as I'm not entirely sure how to do it