Let P=(3,0,2), Q=(1,2,-1), R=(2,-1,1)

a)Find a nonzero vector perpendicular to the triangle with vertices P,Q,R

b)show if u(vector) and v(vector) are orthogonal vectors in R^3 then IIu+vII^2 = IIuII^2 + IIvII^2

please give explanations.

many thanks