This is not a standard parabola!
Geometry
Level
2
A point lies on a parabola whose
- focus is at
- axis of symmetry is parallel to the -axis;
- vertex lies on the -axis.
Find the length of the latus rectum of this parabola.
The answer is 4.
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1 solution
Since focus is (a,3) ,axis parallel to x axis and vertex also lies on y axis therefore the vertex is (0,3).
Equation of parabola is therefore ( y − 3 ) 2 = 4 a x .
P (1,5) lies on it
( ( 5 ) − 3 ) 2 = 4 a ( 1 )
4=4a
Ans. 4