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Show that the Function G (X) = X − [X] is Discontinuous at All Integral Points. Here [X] Denotes the Greatest Integer Function.

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प्रश्न

Show that the function g (x) = x − [x] is discontinuous at all integral points. Here [x] denotes the greatest integer function.

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उत्तर

Given: `g(x)=x-[x]`

It is evident that g is defined at all integral points.

Let \[n \in Z\] .

Then, 

`g(n)=n-[n]=n-n=0`

The left hand limit of at x = n is,

`lim_(x->n^-)g(x)=lim_(x->n^_)(x-[x])=lim_(x->n^_)(x) -lim_(x->n^_)[x]=n-(n-1)=1`

The right hand limit of f at n is, 

`lim_(x->n^+)g(x)=lim_(x->n^+)(x-[x])=lim_(x->n^+)(x)-lim_(x->n^+)[x]=n-n=0`

It is observed that the left and right hand limits of f at x = n do not coincide.

i.e.

\[\lim_{x \to n^-} g\left( x \right) \neq \lim_{x \to n^+} g\left( x \right)\]

So, f is not continuous at x = n,

\[n \in Z\]

Hence, g is discontinuous at all integral points.

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अध्याय 8: Continuity - Exercise 9.2 [पृष्ठ ३७]

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आर.डी. शर्मा Mathematics Volume 1 and 2 [English] Class 12
अध्याय 8 Continuity
Exercise 9.2 | Q 12 | पृष्ठ ३७

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