
is defined as
is defined as : 

putting the value y=c into parabola,we get
x2=c-1
or x2-(c-1)=0
here discriminat=
line y=c is tangent when discriminant is equal to 0.
putting disriminant =0 we get c=1.
(0, c) will be a point on the parabola.

is equal to
General equation of the sphere is ---------------------1)
Since 1) passes through the point (0,0,0) using this in 1) we get d=0
Similarly 1) passes through ( a , 0 , 0 ) , ( 0 , b , 0 ) ( 0 , 0 , c ) using these values in 1)
But as abc0 So , a 0 ,b 0 ,c 0
So from above equations , we have a = - 2g , b= - 2f , c = -2h
centre is (-f ,-g , -h) = ( a/2 , b/2 , c/2 )