Questions in 3-d

Select	Question
	A point moves so that the sum of its distances from the points (4, 0, 0) and (–4, 0, 0) remains 10. The locus of the point is
	A point moves so that the sum of the squares of its distances from two given points remains constant. The locus of the point is
	The equation ${{x}^{2}}+{{y}^{2}}+{{z}^{2}}=0$represents
	The locus of the equation ${{x}^{2}}+{{y}^{2}}+{{z}^{2}}+1=0$is
	The centre of sphere passes through four points (0, 0, 0), (0, 2, 0), (1, 0, 0) and (0, 0, 4) is
	The equation of the sphere touching the three co-ordinate planes is
	Let (3, 4, –1) and (–1, 2, 3) are the end points of a diameter of sphere. Then the radius of the sphere is equal to
	Co-ordinate of a point equidistant from the points (0,0,0), (a, 0, 0), (0, b, 0), (0, 0, c) is
	How many different sphere of radius ‘r’ can be drawn which touches all the three co-ordinate axes
	A plane passes through a fixed point $(p,q,r)$ and cut the axes in A,B,C. Then the locus of the centre of the sphere $OABC$ is