If $$P=(x, y)$$, $${F_1} = \left( {3,0} \right),\,{F_2} = \left( { - 3,0} \right)$$ and $$16{x^2} + 25{y^2} = 400,$$ then $$P{F_1} + P{F_2}$$ equals
A
$$8$$
B
$$6$$
C
$$10$$
D
$$12$$
2
IIT-JEE 1998
MCQ (Single Correct Answer)
The number of values of $$c$$ such that the straight line $$y=4x + c$$ touches the curve $$\left( {{x^2}/4} \right) + {y^2} = 1$$ is
A
$$0$$
B
$$1$$
C
$$2$$
D
infinite.
3
IIT-JEE 1995 Screening
MCQ (Single Correct Answer)
The radius of the circle passing through the foci of the ellipse $${{{x^2}} \over {16}} + {{{y^2}} \over 9} = 1$$, and having its centre at $$(0, 3)$$ is
A
$$4$$
B
$$3$$
C
$$\sqrt {{1 \over 2}} $$
D
$${{7 \over 2}}$$
4
IIT-JEE 1995 Screening
MCQ (Single Correct Answer)
Consider a circle with its centre lying on the focus of the parabola $${y^2} = 2px$$ such that it touches the directrix of the parabola. Then a point of intersection of the circle and parabola is