Equation of the plane such that foot of altitude drawn from (-1, 1, 1) to the plane has the coordinate (3, -2, -1), is:

4x - 3y – 2z = 20

Clearly, the direction ratio of the plane are

4, –3, –2

Thus equation of plane will be

4x – 3y – 2z = d

It will necessarily pass through (3, –2, –1)

i.e,, d = 12 + 6 + 2 = 20

Thus the equation of plane is

4x – 3y – 2z = 20