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GATE 2024 ST – Question 47

Calculus · Single Variable Calculus · 2 marks · Multiple select

Continuous f:[−2,2]→ℝ satisfies which statements?

  1. F(x)=∫₀ˣf(t)dt on [0,2] is differentiable on (0,2).
  2. For any ten points x₁,…,x₁₀ there is x₀ with f(x₀)=[Σf(x_i)]/10.
  3. f is bounded on [−2,2].
  4. If f is differentiable at 0 and f(0)=0, then lim_(x→0)[f(x)+f(x/2)+⋯+f(x/10)]/x=10f′(0).

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Show answer and explanation

Correct answer: (A) F(x)=∫₀ˣf(t)dt on [0,2] is differentiable on (0,2).; (B) For any ten points x₁,…,x₁₀ there is x₀ with f(x₀)=[Σf(x_i)]/10.; (C) f is bounded on [−2,2].

Explanation

A follows from the fundamental theorem of calculus. The average in B lies between the minimum and maximum of continuous f, so the intermediate value theorem gives x₀. Compactness gives boundedness C. For D each term f(x/k)/x→f′(0)/k, giving the harmonic sum (1+1/2+⋯+1/10)f′(0), not generally 10f′(0). **A,B,C**.

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