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Find all points of discontinuity of f, where f is defined by f(x)={x+1ifx≥1x2+1ifx<1 - Mathematics

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Question

Find all points of discontinuity of f, where f is defined by `f (x) = {(x+1, if x>=1),(x^2+1, if x < 1):}`

Sum

Solution

`f (x) = {(x+1, if x>=1),(x^2+1, if x < 1):}`

For x > 1, f(x) = x + 1 and

x < 1, f(x) = x2 + 1 is a polynomial function

So this is the function.

⇒ At x = 1,

`lim_(x -> 1^-)` f(x) = `lim_(x -> 1^-)` (x2 + 1)

`= lim_(h -> 0) [(1 - h)^2 + 1]`

`= lim_(h -> 0) [1 + h^2 - 2h + 1]`

`= lim_(h -> 0) [2 + h^2 - 2h]`

= 2 + 0 - 0

= 2

`lim_(x -> 1^+)` f(x) = `lim_(x -> 1^+)` (x + 1)

= `lim_(h -> 0)` (1 + h + 1)

= `lim_(h -> 0)` (2 + h) = 2 + 0  = 2

f(1) = 1 + 1 = 2

Hence, f is a function at x = 1.

There are no points of discontinuity here.

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Chapter 5: Continuity and Differentiability - Exercise 5.1 [Page 159]

APPEARS IN

NCERT Mathematics [English] Class 12
Chapter 5 Continuity and Differentiability
Exercise 5.1 | Q 10 | Page 159

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