Given that equation is parallel to so that

The normal vector to that plane will be …… (1)

And equation of the plane passing through the point is

a₁(x – x₁) + b₁(y – y₁) + c₁(z – z₁) = 0

and point is (a, b, c) so that,

a₁(x – a) + b₁(y – b) + c₁(z – c) = 0

by equation (1) a_{1 =} b_{1 =} c_{1 =} 1

x + y + z – a – b – c = 0

x + y + z = a + b + c