1.

The points where the function `f(x) = [x] + |1 - x|, -1 < x < 3` where `[.]` denotes the greatest integer function is not differentiable, areA. `(-1,0,1,2,3)`B. `(-1,0,2)`C. `(0,1,2,3)`D. `(-1,0,1,2)`

Answer» Correct Answer - C
We have
`f(x)={{:(,-x,-1 lexlt0),(,1-x,0lexlt1),(,x,1lexlt2),(,1+x,2lexlt3),(,5,x=3):}`
Clearly, f(x) is discontinuous at x=0,1,2 and 3.
So, it is not differentiable at these points.
At x=-1, we have
`underset(x to 1^(+))lim f(x)=underset(x to 1^(+))lim-x=1=f(-1)`
So, it is continuous at x=-1
Also, (RHD at x=1)=-1 (a finite number).
Therefore, f(x) is differentiable at x=-1


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