JEE Advanced 2015Paper 1
- Exam
- JEE Advanced
- Year
- 2015
- Paper
- Paper 1
- Subject
- Mathematics
- Chapter
- Continuity and Differentiability
JEE Advanced 2015 · Paper 1 · Mathematics · Continuity and Differentiability
Let g: ℝ → ℝ be a differentiable function with g(0) = 0, g ^ ′ (0)...
Let g\left(0\right) = 0, {g}^{′}\left(0\right) = 0 and {g}^{′}\left(1\right) \ne 0 .f\left(x\right) = \left\{\right) and h\left(x\right) = {e}^{| x |}x \in \mathbb{R} . denote denote .Then which of the following is (are) true?
Options
- A is differentiable at
- B is differentiable at
- C is differentiable at
- D is differentiable at
Correct answer
A. is differentiable at
Step-by-step solution
f\left(x\right) = \left\{\begin{cases}g\left(x\right) & x > 0 \\ 0 & x = 0 \\ - g\left(x\right) & x < 0\end{cases}\right) <br >LHD: \lim_{x \to {0}^{-}} \left(- {g}^{′}\left(x\right)\right) = - \lim_{x \to {0}^{-}} {g}^{′}\left(x\right) = - 0 = 0RHD: \lim_{x \to {0}^{+}} {g}^{′}\left(x\right) = {g}^{′}\left({0}^{+}\right) = 0f\left(x\right)x = 0h\left(x\right) = {e}^{\left|x\right|} = \left\{\right)
Hence is not differentiable at
f\left(h\left(x\right)\right) = \left\{\dfrac{{e}^{\left|x\right|}}{\left|{e}^{\left|x\right|}\right|}\rightg\left({e}^{\left|x\right|}\right)
f\left(h\left(x\right)\right) = \left\{\begin{cases}g\left({e}^{x}\right) & x \ge 0 \\ g\left({e}^{- x}\right) & x < 0\end{cases}\right) <br >LHD: \lim_{x \to {0}^{+}} {g}^{′}\left({e}^{- x}\right) \times - {e}^{- x} = {g}^{′}\left(1\right) \times - 1 = - {g}^{′}\left(1\right)RHD: \lim_{x \to {0}^{+}} {g}^{′}\left({e}^{x}\right) \times{e}^{x} = {g}^{′}\left(1\right)x = 0h\left(f\left(x\right)\right) = \left\{\right)
= \left\{\begin{cases}1 & x = 0 \\ {e}^{\left|g\left(x\right)\right|} & x \ne 0\end{cases}\right) <br >LHD: \lim_{x \to {0}^{-}} {e}^{\left|g\left(x\right)\right|} \times \pm {g}^{′}\left(x\right) = {e}^{\left|g\left({0}^{-}\right)\right|} \times \pm \left({g}^{′}\left({0}^{-}\right)\right) = 0RHD: \lim_{x \to {0}^{+}} {e}^{\left|g\left(x\right)\right|} \times \pm {g}^{′}\left(x\right) = {e}^{\left|g\left({0}^{+}\right)\right|} \times \pm {g}^{′}\left({0}^{+}\right) = 0
Hence is not differentiable at
f\left(h\left(x\right)\right) = \left\{\dfrac{{e}^{\left|x\right|}}{\left|{e}^{\left|x\right|}\right|}\rightg\left({e}^{\left|x\right|}\right)
f\left(h\left(x\right)\right) = \left\{\begin{cases}g\left({e}^{x}\right) & x \ge 0 \\ g\left({e}^{- x}\right) & x < 0\end{cases}\right) <br >LHD: \lim_{x \to {0}^{+}} {g}^{′}\left({e}^{- x}\right) \times - {e}^{- x} = {g}^{′}\left(1\right) \times - 1 = - {g}^{′}\left(1\right)RHD: \lim_{x \to {0}^{+}} {g}^{′}\left({e}^{x}\right) \times{e}^{x} = {g}^{′}\left(1\right)x = 0h\left(f\left(x\right)\right) = \left\{\right)
= \left\{\begin{cases}1 & x = 0 \\ {e}^{\left|g\left(x\right)\right|} & x \ne 0\end{cases}\right) <br >LHD: \lim_{x \to {0}^{-}} {e}^{\left|g\left(x\right)\right|} \times \pm {g}^{′}\left(x\right) = {e}^{\left|g\left({0}^{-}\right)\right|} \times \pm \left({g}^{′}\left({0}^{-}\right)\right) = 0RHD: \lim_{x \to {0}^{+}} {e}^{\left|g\left(x\right)\right|} \times \pm {g}^{′}\left(x\right) = {e}^{\left|g\left({0}^{+}\right)\right|} \times \pm {g}^{′}\left({0}^{+}\right) = 0