`x^2+y^2+z^2-2x+4y-4z-25=0`
`<=> x^2 -2x + 1 + y^2 +4y +4 +z^2 -4z +4 -34=0`
`<=> (x-1)^2 + (y+2)^2 +(z-2)^2 =34`
`=> I ( 1;-2;2)`
`R =` $\sqrt[]{34}$
* `I ( (-2)/(-2);(4)/(-2);(-4)/(-2))`
`I ( 1;-2;2)`
` R =` $\sqrt[]{1^2+2^2+2^2+25}$ `=`$\sqrt[]{34}$