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महाराष्ट्र राज्य शिक्षण मंडळएचएससी विज्ञान (सामान्य) इयत्ता ११ वी

Evaluate the following limit : If limx→5[xk-5kx-5] = 500, find all possible values of k.

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प्रश्न

Evaluate the following limit : 

If `lim_(x -> 5) [(x^"k" - 5^"k")/(x - 5)]` = 500, find all possible values of k.

बेरीज
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उत्तर

`lim_(x -> 5) [(x^"k" - 5^"k")/(x - 5)]` = 500

∴ k(5)k–1 = 500    ...`[because lim_(x -> "a") (x^"n" - "a"^"n")/(x - "a") = "na"^("n" - 1)]`

∴ k(5)k–1 = 4 × 125

∴ k(5)k–1 = 4 × (5)3

∴ k(5)k–1 = 4 × (5)4–1

Comparing both sides, we get

k = 4

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पाठ 7: Limits - Exercise 7.1 [पृष्ठ १३९]

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