Let P be an arbitrary point having sum of the squares of the distance from the planes $\mathrm{x}+\mathrm{y}+\mathrm{z}=0, l \mathrm{x}-\mathrm{nz}=0$ and $\mathrm{x}-2 \mathrm{y}+\mathrm{z}=0$, equal to 9 . If the locus of the point P is $\mathrm{x}^2+\mathrm{y}^2 +\mathrm{z}^2=9$, then the value of $l-\mathrm{n}$ is equal to $\_\_\_\_$ .