Let P be the plane 2x-y+3z = 42 and let L be the line through (1,2,0)
perpendicular to P. Find the point of intersection of L and P.


answer
Normal to place is <2, -1, 3> so parameteric equations of L are
	x = 1 + 2 t
	y = 2 - t
	z = 0 + 3 t

plugging into P yields

    2(1+2t) -(2-t) +3(3t) = 42
                      14t = 42
                        t = 3

so the point is (7, -1, 9)