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महाराष्ट्र राज्य शिक्षण मंडळएचएससी विज्ञान (सामान्य) इयत्ता ११ वी

Evaluate the following limit : limx→7[x3-343x-7]

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प्रश्न

Evaluate the following limit :

`lim_(x -> 7) [(x^3 - 343)/(sqrt(x) - sqrt(7))]`

बेरीज
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उत्तर

`lim_(x -> 7) [(x^3 - 343)/(sqrt(x) - sqrt(7))]`

= `lim_(x -> 7)[(((x^3 - 343)/(x - 7)))/(((sqrt(x) - sqrt(7))/(x - 7)))]    ...[(because x -> 7","  x ≠ 7),(therefore x - 7 ≠ 0)]`

= `(lim_(x -> 7) ((x^3 - 7^3)/(x - 7)))/(lim_(x -> 7) ((x^(1/2) - 7^(1/2))/(x - 7))`

= `(3*(7)^2)/((1)/(2)*(7)^(-1/2))    ...[because  lim_(x -> "a") (x^"n" - "a"^"n")/(x - "a") = "na"^("n" - 1)]`

= `6*(7)^(5/2)`

= `6 xx 7^2 xx sqrt(7)`

= `294sqrt(7)`.

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पाठ 7: Limits - Exercise 7.1 [पृष्ठ १३९]

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