Sarkari RiseLogin
NDA 2026 · PYQ · Quadratic Equations · hard

If the highest degree coefficient is equal to 1, then what is the total number of quadratic equations which are unchanged on squaring their roots?

  1. A.6
  2. B.4✓ Correct
  3. C.2
  4. D.None

Explanation

Let roots be α, β. After squaring, roots are α², β². For unchanged equation, {α, β} = {α², β²}. Cases: (i) α = α², β = β² gives α, β ∈ {0, 1}, yielding pairs (0,0), (0,1), (1,1) — three equations: x², x(x−1), (x−1)². (ii) α = β², β = α² with α ≠ α²: α = α⁴ gives α³ = 1, α ≠ 1, so α is a primitive cube root of unity. This gives one equation x² + x + 1 = 0. Total = 3 + 1 = 4.
💡 Practice unlimited NDA PYQs + AI-tracked progress on each topic. Sign up free →

More Quadratic Equations questions

Want more NDA practice?

Free daily 10-Q quiz · adaptive mocks · 4,000+ verified PYQs · AI doubt solver in Hindi + English

Sign up freeMore Quadratic Equations practice