vikas askiitian expert
Last Activity: 13 Years ago
distance of vertex from focus & directrix is same ...if parabola is considered in +xy plane then
vertex is at 21/2 away from origin ....
(x2,y2) are coordinates of vertex then
y2-y1/sin@ = x2-x1/cos@ = d ................1
d = 21/2 , (x1,y1) = (0,0) & cos@ = 1/21/2 (coz slope is 1) so
y2 = 1 , x2 = 1
vertex = (1,1)
now focus by same formula 1 will be
focus = (2,2)
directrix will be perpendicular line to axis of parabola passing through origin
y = -x will be directrix
distance of focus from directrix = distance of any point on parabola to focus
(y+x)/root2 = [ (x-2)2+(y-2)2 ]1/2
y2 + x2 + 2xy = 2 [ x2 + y2 - 4x - 4y + 8 ]
x2+y2 -2xy = (8x+8y-16)
(x-y)2 = 8(x+y-2)
this is the required eq ... option A) is correct
approve if u like my ans