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If f(x) =5x+5-x-2x2,for x≠0=k, for x=0} is continuous at x = 0, find k - Mathematics and Statistics

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प्रश्न

If f(x)  `{:(= (5^x + 5^(-x) - 2)/(x^2)"," , "for"  x ≠ 0),(= k",",  "for"  x = 0):}}` is continuous at x = 0, find k

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उत्तर

f(0) = k    ...(Given)  ...(1)

`lim_(x -> 0) "f"(x) =  lim_(x -> 0) (5^x + 5^(-x) - 2)/(x^2)`

= `lim_(x -> 0) (5^x(5^x + 5^(-x) - 2))/(5^x * x^2)`

= `lim_(x -> 0) ((5^x)^2 + 1 - 2*5^x)/(5^x * x^2)`

= `lim_(x -> 0) (5^x - 1)^2/(5^x * x^2)`

= ` lim_(x -> 0) ((5^x - 1)/x)^2 1/5^x`

= `(lim_(x -> 0) (5^x - 1)/x)^2 xx 1/(lim_(x -> 0) 5^x`

= `(log5)^2 xx 1/5^0    ...[because lim_(x -> 0) ("a"^x - 1)/x = log "a"]`

= (log 5)2   ...(2)

Since f is continuous at x = 0,

f(0) = `lim_(x -> 0) "f"(x)`

∴∴k = (log 5)2    ...[By (1) and (2)]

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  क्या इस प्रश्न या उत्तर में कोई त्रुटि है?
अध्याय 8: Continuity - EXERCISE 8.1 [पृष्ठ १७४]

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बालभारती Mathematics and Statistics 2 (Arts and Science) [English] Standard 11 Maharashtra State Board
अध्याय 8 Continuity
EXERCISE 8.1 | Q 11) (ii) | पृष्ठ १७४

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