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Question: If \| z<sup>2</sup> – 1\| = \| z \|<sup>2</sup> + 1 then z lies on a –...

If | z2 – 1| = | z |2 + 1 then z lies on a –

A

Circle

B

Parabola

C

Ellipse

D

None of these

Answer

None of these

Explanation

Solution

Sol. On putting z = x + iy the equation is same as

| x2 – y2 + 2ixy – 1| = x2 + y2 + 1

Ž (x2 – y2 – 1)2 + 4x2y2 = (x2 + y2 + 1)2

Ž x = 0

Ž z lies on imaginary axis, so (A), (B), (C) are ruled out.