1. Given the points O (0, 0, 0), P (2, 6, −1), Q (1, 1, 1) and R (4, 6, 2), find a vector that is perpendicular to both

(a)OPandOQ(b)PQandQR(c)RPandQR

2. Find an equation of the plane passing through point P and having vector n as a normal.

P (−1, 3, −2); n = (-2,1,-1)

3. Find an equation of the plane that passes through the given points.

P (5, 4, 3), Q (4, 3, 1), R (1, 5, 4)