Question:

Let the function, ƒ:[-7, 0]\( \to \)R be continuous on [-7,0] and differentiable on (-7, 0). If ƒ(-7) = - 3 and ƒ'(x) \( \le \) 2, for all x \( \in \) (-7,0), then for all such functions ƒ, ƒ(-1) + ƒ(0) lies in the interval:

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Apply the Mean Value Theorem on [-7, -1] and [-7, 0] to bound f(-1) and f(0) from above; there is no lower bound.
Updated On: Oct 31, 2026
  • \( \left[ { - 6,20} \right] \)
  • \( \left( { - \infty ,\left. {20} \right]} \right. \)
  • \( \left[ { - 3,11} \right] \)
  • \( \left( { - \infty ,\left. {11} \right]} \right. \)
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The Correct Option is B

Solution and Explanation

By the MVT, \(\dfrac{f(-1)-f(-7)}{6}=f'(c)\le2\Rightarrow f(-1)\le-3+12=9\).
Similarly \(\dfrac{f(0)-f(-7)}{7}\le2\Rightarrow f(0)\le-3+14=11\).
So \(f(-1)+f(0)\le20\). There is no lower bound since f' can be very negative (f can decrease without limit). The upper value 20 is attained for \(f(x)=2x+11\).
So \(f(-1)+f(0)\in(-\infty,20]\).
Answer: (B) \((-\infty,20]\)
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