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Examine whether the function is continuous at the points indicated against them : f(x) =x2+18x-19x-1, for x≠1=20, for x=1} at x = 1

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Question

Examine whether the function is continuous at the points indicated against them :

f(x) `{:( = (x^2 + 18x - 19)/(x - 1)",",  "for"  x ≠ 1),(= 20",",  "for"  x = 1):}}` at x = 1

Sum
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Solution

`lim_(x -> 1) "f"(x) =  lim_(x -> 1) (x^2 + 18x - 19)/(x - 1)`

= `lim_(x -> 1) (x^2 + 19x - x - 19)/(x - 1)`

= `lim_(x -> 1) (x(x + 19) - 1(x + 19))/((x - 1))`

= `lim_(x -> 1) ((x - 1)(x + 19))/((x - 1))`

= `lim_(x -> 1)(x + 19)`   ...[∵ x → 1, ∴ x ≠ 1, ∴ x – 1 ≠ 0]

= 1 + 19

= 20

Also, f(1) = 20

∴ `lim_(x -> 1) "f""(x)` = f(1)

∴ f(x) is continuous at x = 1.

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Chapter 8: Continuity - EXERCISE 8.1 [Page 172]

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