Page 77 - Mathematics Class - XI

Viva-Voce

1. Define parabola.
Ans. A parabola is the set of all points in a plane that are equidistant from a fixed line (called directrix) and fixed
point (called focus) in the plane.
2. What is meant by focus of the parabola?
Ans. The fixed point in the interior of a parabole on its axis of symmetry, such that the parabola is the locus of
points equidistant from it (as well as directrix), is called focus of parabola.
3. State the equation of the parabola whose focus is (a, 0) and directrix is x = –a (where a > 0).

Ans. y = 4ax
2
4. What is meant by focal chord of a parabola?
Ans. Any chord passing through the focus of a parabola is called its focal chord.
5. What is the length of latus-rectum of parabola?
Ans. 4a.

6. If the equation of parabola y = 4ax is considered then what will be the equation of latus-rectum?
2
Ans. x = a
7. What is the valve of eccentricity (e) of parabola?

Ans. e = 1

MCQs

1. Parabola y = x is symmetric about
2
a) x-axis b) line y = x c) y-axis d) line y = –x
2. The directrix of the parabola y = 16x is
2
a) x = –4 b) y = –4 c) x = 4 d) y = 4
3. The location of point (1, 2) with respect to parabola y = 8x
2
a) Outside of parabola b) Above part of parabola

c) Inner of parabola d) None of these
4. If parabola is passing through the point (3, 2) then latus-rectum is

a) 1 b) 2 c) 1 d) 4
3 3 3
5. If the parabola has its vertex at point (–3, 0) and the equation of directrix is x + 5 = 0 then the equation of it
a) y = 8 (x + 3) b) y = 8 (x + 5) c) y = –8 (x + 3) d) x = 8 (y + 3)
2
2
2
2
Answers: 1. a) x-axis 2. a) x = –4 3. c) Inner of parabola
4. d) 4 5. a) y = 8 (x + 3)
2
3
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