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Complex Numbers and Quadratic Equations

JEE Main 2025 (Online) 7th April Evening ShiftNumericalMedium📈 Topic in 26% papers+4
Ques. 1JEE Main 2025, 7 April (Evening Shift)

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 .

Answer

98

Solution

Put h = t + 1; as t -1+, h 0+ and t + 2 = 1 + h.

For small h, (1 + h)1/n - 1 hn, i.e. h 0 (1 + h)1/n - 1h = 1n

Divide the equation by h ( 0) and let h 0+:

17x2 + 16x + 121 = 0

6x2 + 7x + 2 = 0 (multiplying by 42)

(2x + 1)(3x + 2) = 0 x = - 12, - 23

a + b = - 76

72(a + b)2 = 72 4936 = 98

Answer: 98

Keep practising — Complex Numbers and Quadratic Equations

Ques. 2JEE Main 2025, 4 April (Morning Shift)

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
Ques. 3JEE Main 2025, 4 April (Morning Shift)

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 .

Ques. 4JEE Main 2025, 4 April (Evening Shift)

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
Ques. 5JEE Main 2025, 4 April (Evening Shift)

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

Ques. 6JEE Main 2025, 3 April (Morning Shift)

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
Ques. 7JEE Main 2025, 3 April (Morning Shift)

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
Ques. 8JEE Main 2025, 3 April (Evening Shift)

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
Ques. 9JEE Main 2025, 3 April (Evening Shift)

Let the equation x(x + 2)(12 - k) = 2 have equal roots. Then the distance of the point (k, k2 ) from the line 3x + 4y + 5 = 0 is

  1. 15
  2. 12
  3. 5 3
  4. 15 5
Ques. 10JEE Main 2025, 2 April (Morning Shift)

Let z be a complex number such that |z| = 1. If 2 + k2 zk + z = kz, k R, then the maximum distance of k + ik2 from the circle |z - (1 + 2i)| = 1 is :

  1. 5 + 1
  2. 3
  3. 3 + 1
  4. 2
Ques. 11JEE Main 2025, 2 April (Morning Shift)

Let Pn = n + n, n N. If P10 = 123, P9 = 76, P8 = 47 and P1 = 1, then the quadratic equation having roots 1 and 1 is :

  1. x2 + x - 1 = 0
  2. x2 - x + 1 = 0
  3. x2 + x + 1 = 0
  4. x2 - x - 1 = 0

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