1. ## determine equation

determine the Cartesian equation of a plane that passes through the points $\displaystyle (1,4,5)$ and $\displaystyle (3,2,1)$ and is perpendicular to the plane $\displaystyle 2x-y+z-1=0$

2. How about Ax + By + Cz + D = 0?

Then 2A - B + C = 0

Then A + 4B + 5C + D = 0

Then 3A + 2B + 1C + D = 0

What else is needed?