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12th Grade > Mathematics

INTRODUCTION TO CONICS AND PARABOLA MCQs

Total Questions : 14 | Page 2 of 2 pages
Question 11. The co-ordinates of the extremities of the latus rectum of the parabola 5y2=4x are 
  1.    (15.25),(−15,25)
  2.    (15.25),(15,−25)
  3.    (15.45),(15,−45)
  4.    None of these
 Discuss Question
Answer: Option B. -> (15.25),(15,−25)
:
B
y2=4.15x;a=15. Focus is (15,0) and co-ordinates of latus rectum are y2=425y=±25
or end points of latus rectum are (15,±25) .
Question 12. A parabola passing through the point (-4,-2) has its vertex at the origin and y-axis as its axis. The latus rectum of 
the parabola is 
  1.    6
  2.    8
  3.    10
  4.    12
 Discuss Question
Answer: Option B. -> 8
:
B
Let the equation of parabola is x2=4ay, but a = 42=2.Thenequationisx2=8y and latus rectum = 4a = 8
Question 13. The points on the parabola y2=36x whose ordinate is three times the absicca are 
  1.    (0, 0), (4, 12)
  2.    (1, 3), (4, 12)
  3.    (4, 12)
  4.    None of these
 Discuss Question
Answer: Option A. -> (0, 0), (4, 12)
:
A
y1=3x1 . According to given condition 9x21=36x1
x1=4,0y1=12,0
Hence the points are (0,0) and (4,12).
Question 14. The equation of the parabola with its vertex at the origin, axis on the y-axis and passing through the point (6, -3) is   
  1.    y3=12x+6 
  2.    x2=12y 
  3.    x2=−12y 
  4.    y2=−12x+6 
 Discuss Question
Answer: Option C. -> x2=−12y 
:
C
Since the axis of parabola is y-axis
Equation of parabola x2=4ay
Since it passes through (6 , -3)
36 = -12 a a=3
Equation of parabola is x2=12y .

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