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Evaluate the following : Given that 7x ≤ f(x) ≤ 3x2 – 6 for all x. Determine the value of flimx→3f(x)

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Question

Evaluate the following :

Given that 7x ≤ f(x) ≤ 3x2 – 6 for all x. Determine the value of `lim_(x -> 3) "f"(x)`

Sum
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Solution

It is given that

7x ≤ f(x) ≤ 3x2 – 6 for all x

∴ `lim_(x -> 3) 7x ≤  lim_(x -> 3) "f"(x) ≤  lim_(x -> 3) (3x^2 - 6)`

∴ `7(3) ≤  lim_(x -> 3) "f"(x) ≤ 3(9) - 6`

∴ `21 ≤  lim_(x -> 3) "f"(x) ≤ 21`

By squeeze theorem, `lim_(x -> 3) "f"(x)` = 21.

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Chapter 7: Limits - Miscellaneous Exercise 7.2 [Page 159]

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