Question

What is the distance between plane x+y+z=1 from the point (1,-1,1)?

Answer 1

use this formula:

$D = \frac{A x_{1} + B y_{1} + C z_{1} + d}{ \sqrt{ A^{2} + B^{2} + C^{2} } }$

here x1, y1, z1 are the given points(i.e. (1,-1,1)) and A, B and C are the direction ratios(i.e. 1, 1, 1).

Hope this helps.