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Joint Entrance Examination
Mathematics
Limits, Continuity and Differentiability
Question 371
Question 371 of 401
Medium
MCQ
Let
f
f
f
and
g
g
g
A
continuous everywhere but not differentiable at \[x=1\]
B
differentiable everywhere
C
not continuous at \[x=-1\]
D
continuous everywhere but not differentiable exactly at one point
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Official solution
\[
\begin{aligned} & \text { Sol. } f(x)=\left\{\[\begin{gathered} x+1, x<0 \\ \ 1-x, 0 \leq x<1 \\ x-1,1 \leq x \end{gathered}\end{aligned}
\]\right. \\\\ \& g(x)=\left\{\[\begin{gathered} x+1, x<0 \\ 1, x \geq 0 \end{gathered}\]\right. \\\\ \& g(f(x))=\left\{\[\begin{gathered} x+2, x<-1 \\ 1, x \geq-1 \end{gathered}\]\right. \]
∴
g
(
f
(
x
)
)
\therefore \mathrm{g}(\mathrm{f}(\mathrm{x}))
∴
g
(
f
(
x
))
is continuous everywhere
g
(
f
(
x
)
)
\mathrm{g}(\mathrm{f}(\mathrm{x}))
g
(
f
(
x
))
is not differentiable at
x
=
−
1
\mathrm{x}=-1
x
=
−
1
Differentiable everywhere else.
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