A. 1

B. -1

C. 21

D. 16

The equation to the circles whose radius is 3 and which touches internally the circle x^{2}+y^{2}-4x+6y-12=0 at he point (-1, 1) is

The equation of the chord of contact of the point (4, 2) with respect to the circle x^{2}+y^{2}-5x+4y-3=0 is

The two circles x^{2}+y^{2}=a^{2}, x^{2}+y^{2}=c^{2}(c>0) touch each other if

The area of the quadrilateral formed by the tangents from the point (4,5) to the circle x^{2}+y^{2}-4x-2y-11=0 with a pair of radii joining the points of contact of these tangents is

The equation of the normal to the curve (x/a)^{2/3}+(y/b)^{2/3}=1 at (a cos^{3}θ, b sin^{3}θ ) is