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Complex Numbers and Quadratic Equations · Question 41

JEE Main 2025 (Online) 7th April Morning ShiftMCQMedium📈 Topic in 45% papers+4−1
1

Among the statements (S1) : The set \z C - \-i\ : |z| = 1 and z - iz + i is purely real \ contains exactly two elements, and (S2) : The set \z C - \-1\ : |z| = 1 and z - 1z + 1 is purely imaginary \ contains infinitely many elements.

  1. both are incorrect
  2. both are correct
  3. only (S2) is correct
  4. only (S1) is correct

Answer

(3) only (S2) is correct

Solution

(S1): z - iz + i is real z, i and −i are collinear z lies on the imaginary axis.

With |z| = 1: z = i or z = -i; but z -i.

the set is \i\ (one element only). (S1) is incorrect.

(S2): Let z = + i , .

z - 1z + 1 = ei - 1ei + 1 = ei /2 - e-i /2ei /2 + e-i /2 = i 2

purely imaginary for every (- , ), 0 — infinitely many z. (S2) is correct.

Answer: (3)

JEE Main 2025 (Online) 7th April Morning Shift

Keep practising — Complex Numbers and Quadratic Equations

2

If the locus of z C, such that Re ( z-12z+i ) + Re ( z-12 z-i ) = 2, is a circle of radius r and center (a, b), then 15abr2 is equal to :

  1. 16
  2. 24
  3. 12
  4. 18
JEE Main 2025 (Online) 7th April Evening Shift
3

The number of real roots of the equation x|x-2| + 3|x-3| + 1 = 0 is :

  1. 4
  2. 3
  3. 2
  4. 1
JEE Main 2025 (Online) 7th April Evening Shift
4

For t > -1, let t and t be the roots of the equation ((t + 2)1/7 - 1 )x2 + ((t + 2)1/6 - 1 )x + ((t + 2)1/21 - 1 ) = 0 If t -1+ t = a and t -1+ t = b, then 72(a + b)2 is equal to .

JEE Main 2025 (Online) 7th April Evening Shift
5

Consider the equation x2 + 4x - n = 0, where n [20, 100] is a natural number. Then the number of all distinct values of n, for which the given equation has integral roots, is equal to

  1. 6
  2. 5
  3. 8
  4. 7
JEE Main 2025 (Online) 4th April Morning Shift
6

Let A = \z C : |z - 2 - i| = 3\, B = \z C : Re(z - iz) = 2\ and S = A B. Then z S |z|2 is equal to .

JEE Main 2025 (Online) 4th April Morning Shift
7

Let the product of 1 = (8 + i) + (7 + 4i) and 2 = (1 + 8i) + (4 + 7i) be + i , i = -1. Let p and q be the maximum and the minimum values of + respectively. Then p + q is equal to :

  1. 130
  2. 150
  3. 160
  4. 140
JEE Main 2025 (Online) 4th April Evening Shift
8

If is a root of the equation x2+x+1=0 and k=1n ( k+ 1 k )2=20, then n is equal to .

JEE Main 2025 (Online) 4th April Evening Shift
9

Let and be the roots of x2 + 3x - 16 = 0, and and be the roots of x2 + 3x - 1 = 0. If Pn = n + n and Qn = n + n, then P25 + 3P242P23 + Q25 - Q23Q24 is equal to

  1. 4
  2. 3
  3. 5
  4. 7
JEE Main 2025 (Online) 3rd April Morning Shift
10

Let z C be such that z2+3iz-2+i = 2+3i. Then the sum of all possible values of z2 is :

  1. -19+2i
  2. -19-2i
  3. 19-2i
  4. 19+2i
JEE Main 2025 (Online) 3rd April Morning Shift
11

If z1, z2, z3 C are the vertices of an equilateral triangle whose centroid is z0, then k=13 (zk - z0)2 is equal to

  1. 0
  2. 1
  3. i
  4. -i
JEE Main 2025 (Online) 3rd April Evening Shift

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