The GATE Grind

GATE 2023 MA – Question 41

Ordinary Differential Equations · Higher Order Equations and Systems · 2 marks · Multiple choice

Let φ,ψ be independent solutions of y″+(2−cos x)y=0 on ℝ. Suppose α<β,φ(α)=φ(β)=0 and φ≠0 on (α,β). P:φ′(α)φ′(β)>0. Q:φ(x)ψ(x)≠0 throughout (α,β). Choose truth values.

  1. P true, Q false
  2. P false, Q true
  3. Both false
  4. Both true

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (C) Both false

Explanation

Zeros of a nonzero solution are simple by uniqueness. Its constant sign between consecutive zeros makes its endpoint slopes opposite in sign, so their product is negative. Sturm separation says the independent solution ψ has one zero between consecutive zeros of φ, refuting Q. **C**.

More Higher Order Equations and Systems questions

All Higher Order Equations and Systems questions →