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Complex Numbers and Quadratic Equations

JEE Main 2025 (Online) 23rd January Evening ShiftMCQMedium📈 Topic in 13% papers+4−1
Ques. 1JEE Main 2025, 23 January (Evening Shift)

The number of complex numbers z, satisfying |z|=1 and | z z+ zz |=1, is :

  1. 8
  2. 10
  3. 4
  4. 6

Answer

(1) 8

Solution

|z|=1 means z lies on the unit circle: z=ei .

z z+ zz=2 2 |2 2 |=1 2 = 12

[figure]

2 [0,4 ) covers two turns: 2 = 12 gives 4 points, 2 =- 12 gives 4 points.

8 points ( =30 ,60 ,120 , ,330 )

Answer: (1)

Keep practising — Complex Numbers and Quadratic Equations

Ques. 2JEE Main 2025, 23 January (Evening Shift)

Let , be the roots of the equation x2-ax-b=0 with Im( )<Im( ). Let Pn= n- n. If P3=-5 7 i, P4=-3 7 i, P5=11 7 i and P6=45 7 i, then | 4+ 4 | is equal to .

Ques. 3JEE Main 2025, 22 January (Morning Shift)

Let z1,z2 and z3 be three complex numbers on the circle |z|=1 with (z1)= - 4, (z2)=0 and (z3)= 4. If |z1 z2+z2 z3+z3 z1 |2= + 2, , Z, then the value of 2+ 2 is :

  1. 41
  2. 29
  3. 24
  4. 31
Ques. 4JEE Main 2025, 22 January (Evening Shift)

Let and be the distinct roots of 2x2+( )x-1=0, (0,2 ). If m and M are the minimum and the maximum values of 4+ 4, then 16(M+m) equals :

  1. 27
  2. 17
  3. 25
  4. 24
Ques. 5JEE Main 2025, 22 January (Evening Shift)

Let the curve z(1+i)+ z(1-i)=4, z , divide the region |z-3| 1 into two parts of areas and . Then | - | equals :

  1. 1+ 3
  2. 1+ 6
  3. 1+ 2
  4. 1+ 4

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