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महाराष्ट्र राज्य शिक्षण मंडळएचएससी विज्ञान (सामान्य) इयत्ता ११ वी

The following function has a removable discontinuity? If it has a removable discontinuity, redefine the function so that it become continuous : f(x) =x3-8x2-4, for x>2=3, for x=2=e3(x-2)2-12(x-2)2

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प्रश्न

The following function has a removable discontinuity? If it has a removable discontinuity, redefine the function so that it become continuous :

f(x) `{:(= (x^3 - 8)/(x^2 - 4)",",  "for"  x > 2),(= 3",",  "for"  x = 2),(= ("e"^(3(x - 2)^2 - 1))/(2(x - 2)^2) ",",  "for"  x < 2):}`

बेरीज
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उत्तर

f(2) = 3   ...(Given)

`lim_(x -> 2^-) "f"(x) = lim_(x -> 2^-) (x^3 - 8)/(x^2 - 4)`

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

= `lim_(x -> 2^-) ((x - 2) (x^2 + 2x + 4))/((x - 2)(x + 2))`

= `lim_(x -> 2^-) (x^2 + 2x + 4)/(x + 2)`

= `(lim_(x -> 2^-) (x^2 + 2x + 4))/(lim_(x -> 2^-) (x + 2))`

= `((2)^2 + 2(2) + 4)/(2 + 2)`

= `12/4`

= 3

`lim_(x -> 2^+) "f"(x) = lim_(x -> 2^+) ("e"^(3(x - 2)^2) - 1)/(2(x - 2)^2)`

Put x – 2 = h

∴ x = 2 + h

As x → 2, h → 0

∴ `lim_(x -> 2^+) "f"(x) =  lim_("h" -> 0) ("e"^(3"h"^2) - 1)/(2"h"^2)`

= `1/2 lim_("h" -> 0) ("e"^(3"h"^2) - 1)/(3"h"^2) xx 3`

= `1/2 xx 1 xx 3  ...[(because "h" -> 0  therefore "h"^2 -> 0),(and lim_(x -> 0) ("e"^x - 1)/x = 1)]`

= `3/2`

∴ `lim_(x -> 2^-) "f"(x) ≠ lim_(x -> 2^+) "f"(x)`

∴ `lim_(x -> 2) "f"(x)` does not exist

∴ f(x) is discontinuous at x = 2

This discontinuity is irremovable.

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पाठ 8: Continuity - EXERCISE 8.1 [पृष्ठ १७४]

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