Show that the locus of the points from which the tan- gents to the three spheres (x-2)+y+2=1, x+(y-3)+z=6, (x+2)+(y+1)+(z-2) =6 are all equal is the line x|3==y/2=z/7. Find the coordinates of the point on this line from which the length of the tangents to the three spheres is also equal to that of the tangent to the sphere (2x+1) +4y +(2z-1)=6.