Find the equation of the plane mid parallel to the planes `2x-2y+z+3=0\ a n d\ 2x-2y+z+9=0.`

Explanation

`*` Equation of planes: `pi_{1}=2 x-2 y+z+3=0`


`pi_{2}=2 x-2 y+z+9=0`


Let the equation of the plane mid-parallel to these planes be:


`pi_{3}: 2 x-2 y+z+theta=0`


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