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Complex Numbers and Quadratic Equations

JEE Main 2026 (Online) 28th January Morning ShiftMCQMedium📈 Topic in 40% papers+4−1
Ques. 1JEE Main 2026, 28 January (Morning Shift)

Let z be a complex number such that |z − 6| = 5 and |z + 2 − 6i| = 5. Then the value of z3 + 3z2 - 15z + 141 is equal to :

  1. 61
  2. 37
  3. 42
  4. 50

Answer

(4) 50

Solution

|z − 6| = 5 is a circle with centre (6, 0) and radius 5, and |z + 2 − 6i| = 5 is a circle with centre (−2, 6) and radius 5.

The distance between the centres is 82 + 62 = 10, which equals the sum of the radii, so the circles touch externally at the mid-point of the centres, i.e. z = 2 + 3i.

z2 = 4 - 9 + 12i = -5 + 12i

z3 = (2 + 3i)(-5 + 12i) = -46 + 9i

z3 + 3z2 - 15z + 141

= (-46 + 9i) + (-15 + 36i) - (30 + 45i) + 141

= 50 + 0i

value = 50

Answer: (4)

Keep practising — Complex Numbers and Quadratic Equations

Ques. 2JEE Main 2026, 28 January (Evening Shift)

Let the arithmetic mean of 1a and 1b be 516, a > 2. If is such that a, 4, , b are in A.P., then the equation x2 - ax + 2( - 2b) = 0 has :

  1. one root in (1, 4) and another in (-2, 0)
  2. one root in (0, 2) and another in (-4, -2)
  3. both roots in the interval (-2, 0)
  4. complex roots of magnitude less than 2
Ques. 3JEE Main 2026, 28 January (Evening Shift)

Let A = \z C : |z - 2| 4\ and B = \z C : |z - 2| + |z + 2| = 5\. Then the \|z1 - z2| : z1 A and z2 B\ is :

  1. 172
  2. 8
  3. 9
  4. 152
Ques. 4JEE Main 2026, 24 January (Morning Shift)

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

  1. 3
  2. 2
  3. 5
  4. 4
Ques. 5JEE Main 2026, 24 January (Morning Shift)

Let S = \z C : | z-6iz-2i | = 1 and | z-8+2iz+2i | = 35 \. Then z S |z|2 is equal to :

  1. 413
  2. 398
  3. 385
  4. 423
Ques. 6JEE Main 2026, 24 January (Evening Shift)

The smallest positive integral value of a, for which all the roots of x4 - ax2 + 9 = 0 are real and distinct, is equal to

  1. 7
  2. 3
  3. 4
  4. 9
Ques. 7JEE Main 2026, 24 January (Evening Shift)

Let z = (1 + i)(1 + 2i)(1 + 3i) (1 + ni), where i = -1. If |z|2 = 44200, then n is equal to .

Ques. 8JEE Main 2026, 23 January (Morning Shift)

If α and β (α < β) are the roots of the equation (-2 + 3 ) ( | x - 3 | ) + (x - 6 x ) + (9 - 2 3 ) = 0, x 0, then + is equal to :

  1. 8
  2. 10
  3. 9
  4. 11
Ques. 9JEE Main 2026, 23 January (Morning Shift)

Let S = \z : 3 |2z - 3(1 + i)| 7 \ be a set of complex numbers. Then Minz S | (z + 12(5 + 3i) ) | is equal to :

  1. 12
  2. 52
  3. 2
  4. 32
Ques. 10JEE Main 2026, 23 January (Morning Shift)

A building construction work can be completed by two masons A and B together in 22.5 days. Mason A alone can complete the construction work in 24 days less than mason B alone. Then mason A alone will complete the construction work in :

  1. 36 days
  2. 24 days
  3. 30 days
  4. 42 days
Ques. 11JEE Main 2026, 23 January (Evening Shift)

If z = 32 + i2, i = -1, then (z201 - i )8 is equal to

  1. 1
  2. 0
  3. -1
  4. 256

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