1.

If plane 2x+3y+6z+k=0 is tangent to the sphere x^(2)+y^(2)+z^(2)+2x-2y+2z-6=0, then a value of k is

Answer»

26
16
`-26`
NONE of these

Solution :Center and radius of the sphere are `(-1,1,-1)` and 3, respectively.
Distance of `(-1,1,-1)` from the plane is `|(-2+3-6+k)/SQRT(4+9+36)|`.
Since, the plane is TANGENT to the plane.
`therefore |(k-5)/7|=3`.
`therefore k=-16,26`


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