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Joint Entrance Examination
Mathematics
Complex Numbers
Question 426
Question 426 of 455
Medium
MCQ
If
z
=
x
+
i
y
z=x+i y
z
=
x
+
i
y
satisfies
∣
z
∣
−
2
=
0
|z|-2=0
∣
z
∣
−
2
=
0
and
∣
z
−
i
∣
−
∣
z
+
5
i
∣
=
0
|z-i|-|z+5 i|=0
∣
z
−
i
∣
−
∣
z
+
5
i
∣
=
0
, then :
A
\[x+2 y-4=0\]
B
\[x^{2}+y-4=0\]
C
\[x+2 y+4=0\]
D
\[x^{2}-y+3=0\]
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Official solution
∣
z
−
i
∣
=
∣
z
+
5
i
∣
|z - i| = |z + 5i|
∣
z
−
i
∣
=
∣
z
+
5
i
∣
So, \[\mathrm{z}\] lies on \[{ \bot ^r}\] bisector of
(
0
,
1
)
(0,1)
(
0
,
1
)
and
(
0
,
−
5
)
(0, - 5)
(
0
,
−
5
)
i.e., line
y
=
−
2
y = - 2
y
=
−
2
as
∣
z
∣
=
2
|z| = 2
∣
z
∣
=
2
\[ \Rightarrow z = - 2i\]
x
=
0
x = 0
x
=
0
and
y
=
−
2
y = - 2
y
=
−
2
so,
x
+
2
y
+
4
=
0
x + 2y + 4 = 0
x
+
2
y
+
4
=
0
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