polar(p, A, s)

Write down the equations of the polars of the points (1,2,-1), (3,5,-2) and (0,1/2,-1/2) with respect to the sphere x^2+y^2+z^2- 3*x+y+z-5=0 and show that they form a pencil of planes.

The answers show that three planes p1, p2, and p3 form a pencil of planes.

geom3d[pole]