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JEE Advanced · Mathematics · 3. Complex Numbers

Let s, t, r be non-zero complex numbers and L be the set of solutions z=x+iy x, y, i=-1 of the equation sz+tz-+r=0, where z-=x-iy. Then, which of the following statement(s) is (are) TRUE?

  1. A If L has exactly one element, then st
  2. B If s=t, then L has infinitely many elements
  3. C The number of elements in Lz:z-1+i=5 is at most 2
  4. D If L has more than one element, then L has infinitely many elements
Verified Solution

Answer & Solution

Correct Answer

(A) If L has exactly one element, then st

Step-by-step Solution

Detailed explanation

Given
sz+tz-+r=0 ...(i)
On taking conjugate s-z-+t-z+r-=0 ...(ii)
zs2-t2=r-t-rs-
1 If st then z has unique value
2 If s=t then r-t-rs- may or may not be zero so L may be empty set
3 Locus of z is null set or singleton set or a line in all cases it will intersect given circle at most two points.
4 In this case locus of z is a line so L has infinite elements
From JEE Advanced
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