Question

Find an equation of the plane passing through the points A(1,2,4), B(3,-1,2) and C(2,1,1).

Answer 1

set up a system of equations
find solution using cramers rule which involves finding determinate of a 3X3 matrix

Answer 2

http://en.wikipedia.org/wiki/Plane_%28geometry%29#Method_2

Answer 3

Or between A and B <1-3, 2-(-1), 4-2> and then do the same between A and C. Cross those 2 vectors. That is how you start.

Answer 4

sorry its a little late but just in case you haven't figured it out yet
solution:
7x +4y + z -19 = 0
or
z = -7x -4y +19