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Question
Mathematics
The length of the latus rectum of the parabola 169[(x-1)2+(y-3)2]=(5 x-12 y+ 17) 2 is:
Q. The length of the latus rectum of the parabola
169
[
(
x
−
1
)
2
+
(
y
−
3
)
2
]
=
(
5
x
−
12
y
+
17
)
2
is:
4285
206
BITSAT
BITSAT 2011
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A
13
14
12%
B
13
12
25%
C
13
28
62%
D
None of these
0%
Solution:
Given equation can be rewritten as
(
x
−
1
)
2
+
(
y
−
3
)
2
=
(
13
5
x
−
12
y
+
17
)
2
⇒
SP
=
PM
Here, focus is
(
1
,
3
)
, directrix
5
x
−
12
y
+
17
=
0
∴
the distance of the focus from the directrix
=
∣
∣
25
+
144
5
−
36
+
17
∣
∣
=
13
14
=
2
a
∴
Latusrectum
=
2
×
13
14
=
13
28