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Test the continuity of the following function at the point or interval indicated against them : f(x) =x3-8x+2-3x-2, for x≠2=-24, for x=2} at x = 2

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प्रश्न

Test the continuity of the following function at the point or interval indicated against them :

f(x)  `{:(= (x^3 - 8)/(sqrt(x + 2) - sqrt(3x - 2))",",  "for"  x ≠ 2),(= -24",",  "for"  x = 2):}}` at x = 2

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उत्तर

f(2) = – 24       …(given)

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

= `lim_(x -> 2) (x^3 - 8)/(sqrt(x + 2) - sqrt(3x - 2)) xx (sqrt(x + 2) + sqrt(3x + 2))/(sqrt(x + 2) + sqrt(3x - 2))`

= `lim_(x -> 2) ((x^3 - 8)(sqrt(x + 2) + sqrt(3x - 2)))/((x + 2) - (3x - 2))`

= `lim_(x -> 2) ((x^3 - 2^3)(sqrt(x + 2) + sqrt(3x - 2)))/(-2x + 4)`

= `lim_(x -> 2) ((x - 2)(x^2 + 2x + 4)(sqrt(x + 2) + sqrt(3x  - 2)))/(-2(x - 2))`

= `lim_(x -> 2) ((x^2 + 2x + 4)(sqrt(x + 2) + sqrt(3x - 2)))/(-2)   ...[(becausex -> 2","  x ≠ 2),(therefore x - 2 ≠ 0)]`

= `(-1)/(2) lim_(x -> 2) (x^2 + 2x + 4) (sqrt(x + 2) + sqrt(3x - 2))`

= `(-1)/(2) lim_(x -> 2) (x^2 + 2x + 4) lim_(x -> 2) (sqrt(x + 2) + sqrt(3x - 2))`

= `(-1)/(2) xx [2^2 + 2(2) + 4] xx (sqrt(2  + 2) + sqrt(3(2) - 2))`

= `(-1)/(2) xx 12 xx (2 + 2)`

= – 24

∴ `lim_(x -> 2) "f"(x)` = f(2)

∴ f(x) is continuous at x = 2

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  क्या इस प्रश्न या उत्तर में कोई त्रुटि है?
अध्याय 8: Continuity - EXERCISE 8.1 [पृष्ठ १७३]

APPEARS IN

बालभारती Mathematics and Statistics (Arts and Science) Part 2 [English] Standard 11 Maharashtra State Board
अध्याय 8 Continuity
EXERCISE 8.1 | Q 5) (ii) | पृष्ठ १७३

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