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Joint Entrance Examination
Mathematics
Complex Numbers
Question 351
Question 351 of 455
Easy
MCQ
The conjugate of a complex number is
1
i
−
1
\dfrac1{i-1}
i
−
1
1
. Then that complex number is
A
−
1
i
−
1
\dfrac{-1}{i-1}
i
−
1
−
1
B
1
i
+
1
\dfrac1{i+1}
i
+
1
1
C
−
1
i
+
1
\dfrac{-1}{i+1}
i
+
1
−
1
D
1
i
−
1
\dfrac1{i-1}
i
−
1
1
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Official solution
\[\overline{\left(\frac1{i-1}\right)}=\frac1{\overline{i-1}}=\frac1{-i-1}=\frac{-1}{i+1}.\]
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