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UPSC NDA 2 2021 Mathematics Solved Paper
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© examsnet.com
Question : 14
Total: 120
If
z
=
x
+
i
y
, where
i
=
√
−
1
, then what does the equation
z
z
+
|
z
|
2
+
4
(
z
+
z
)
−
48
=
0
represent?
[NDA-II 2021]
Straight line
Parabola
Circle
Pair of straight lines
Validate
Solution:
👈: Video Solution
(c) Given,
z
=
x
+
i
y
∴
z
=
x
−
i
y
∴
z
+
z
=
2
x
and
|
z
|
2
=
x
2
+
y
2
∴
z
z
+
|
z
|
2
+
4
(
z
+
z
)
−
48
=
0
(
x
+
i
y
)
(
x
−
i
y
)
+
x
2
+
y
2
+
4
(
2
x
)
−
48
=
0
x
2
+
y
2
+
x
2
+
y
2
+
8
x
−
48
=
0
2
x
2
+
2
y
2
+
8
x
−
48
=
0
x
2
+
y
2
+
4
x
−
24
=
0
which represents circle.
Hence, option (c) is correct.
© examsnet.com
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