signSo the points given are A = (5,5,3), B = (2,8,9), and C = (1,0,5) and I have to find the equation of the plane.

I know that in order to do this, you have to find the line that's perpendicular to these vectors and to do that, you can take the cross product of two of them. I decided to use AB and AC.

So here's what I have:

AB = -3i+3j+6k

AC = -4i-5j+2k

AB x AC = 36i-18j+27k -> 36x-18y+27z = 171.