Q. 85.0( 1 Vote )

x + 2y = 4

B. x - y = 3

C. 2x + y = 5

D. X + 3y = 8

Answer :

Given that we need to find the equation of the directrix of a parabola whose focus is (2, 6) and having a vertex at (1, 4).



We know that the directrix is perpendicular to the axis and vertex is the midpoint of focus and the intersection point of axis and directrix.


Let us find the slope of the axis. We know that the slope of the straight line passing through the points (x1, y1) and (x2, y2) is .




m1 = 2.


We know that the product of slopes of the perpendicular lines is - 1.


Let m2 be the slope of the directrix.


m1.m2 = - 1


2×m2 = - 1



Let us assume the intersection point on directrix is (x1, y1).




x1 + 2 = 2 and y1 + 6 = 8


x = 0 and y = 2.


The point on directrix is (0, 2).


We know that equation of the straight line passing through point (x1, y1) and slope m is y - y1 = m(x - x1).



2(y - 2) = - 1(x)


2y - 4 = - x


x + 2y - 4 = 0


The correct option is A

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation
caricature
view all courses
RELATED QUESTIONS :

<span lang="EN-USRD Sharma - Mathematics

Which of thRD Sharma - Mathematics

The focus oRD Sharma - Mathematics

The length RD Sharma - Mathematics

The length RD Sharma - Mathematics

<span lang="EN-USRD Sharma - Mathematics

<span lang="EN-USRD Sharma - Mathematics

<span lang="EN-USRD Sharma - Mathematics

If the coorRD Sharma - Mathematics

If the focuRD Sharma - Mathematics