Composite or piecewise function extremum analysis

The question involves finding extrema or analyzing differentiability and extremal behavior of functions defined piecewise, involving absolute values, or composed with other operations like integrals.

csat-suneung 2011 Q24 4 marks View
There is a quartic function $f ( x )$ with leading coefficient 1, $f ( 0 ) = 3$, and $f ^ { \prime } ( 3 ) < 0$. For a real number $t$, define the set $S$ as $$S = \{ a \mid \text{the function } | f ( x ) - t | \text{ is not differentiable at } x = a \}$$ and let $g ( t )$ be the number of elements in set $S$. When the function $g ( t )$ is discontinuous only at $t = 3$ and $t = 19$, find the value of $f ( - 2 )$. [4 points]
csat-suneung 2013 Q21 4 marks View
For the function $f ( x ) = k x ^ { 2 } e ^ { - x } ( k > 0 )$ and a real number $t$, let $g ( t )$ be the smaller of the distance from the point $( t , f ( t ) )$ on the curve $y = f ( x )$ to the $x$-axis and the distance to the $y$-axis. What is the maximum value of $k$ such that the function $g ( t )$ is not differentiable at exactly one point? [4 points]
(1) $\frac { 1 } { e }$
(2) $\frac { 1 } { \sqrt { e } }$
(3) $\frac { e } { 2 }$
(4) $\sqrt { e }$
(5) $e$
csat-suneung 2016 Q21 4 marks View
For a real number $0 < t < 41$, the curve $y = x ^ { 3 } + 2 x ^ { 2 } - 15 x + 5$ and the line $y = t$ intersect at three points. Let the point with the largest $x$-coordinate be $( f ( t ) , t )$ and the point with the smallest $x$-coordinate be $( g ( t ) , t )$. Let $h ( t ) = t \times \{ f ( t ) - g ( t ) \}$. What is the value of $h ^ { \prime } ( 5 )$? [4 points]
(1) $\frac { 79 } { 12 }$
(2) $\frac { 85 } { 12 }$
(3) $\frac { 91 } { 12 }$
(4) $\frac { 97 } { 12 }$
(5) $\frac { 103 } { 12 }$
csat-suneung 2018 Q29 4 marks View
For two real numbers $a$ and $k$, two functions $f ( x )$ and $g ( x )$ are defined as $$\begin{aligned} & f ( x ) = \begin{cases} 0 & ( x \leq a ) \\ ( x - 1 ) ^ { 2 } ( 2 x + 1 ) & ( x > a ) \end{cases} \\ & g ( x ) = \begin{cases} 0 & ( x \leq k ) \\ 12 ( x - k ) & ( x > k ) \end{cases} \end{aligned}$$ and satisfy the following conditions. (가) The function $f ( x )$ is differentiable on the entire set of real numbers. (나) For all real numbers $x$, $f ( x ) \geq g ( x )$. When the minimum value of $k$ is $\frac { q } { p }$, find the value of $a + p + q$. (Here, $p$ and $q$ are coprime natural numbers.) [4 points]
csat-suneung 2021 Q30 4 marks View
The function $f ( x )$ is a cubic function with leading coefficient 1, and the function $g ( x )$ is a linear function. Define the function $h ( x )$ as $$h ( x ) = \begin{cases} | f ( x ) - g ( x ) | & ( x < 1 ) \\ f ( x ) + g ( x ) & ( x \geq 1 ) \end{cases}$$ If $h ( x )$ is differentiable on the entire set of real numbers, and $h ( 0 ) = 0$, $h ( 2 ) = 5$, find the value of $h ( 4 )$. [4 points]
csat-suneung 2024 Q21 4 marks View
For a positive number $a$, the function $f(x)$ defined on $x \geq -1$ is $$f(x) = \begin{cases} -x^2 + 6x & (-1 \leq x < 6) \\ a\log_4(x-5) & (x \geq 6) \end{cases}$$ For a real number $t \geq 0$, let $g(t)$ denote the maximum value of $f(x)$ on the closed interval $[t-1, t+1]$. If the minimum value of the function $g(t)$ on the interval $[0, \infty)$ is 5, find the minimum value of the positive number $a$. [4 points]
grandes-ecoles 2025 Q9 View
Consider the function $$f(x) := \frac{1}{3}x^3 \quad \text{if } x \geq 0, \quad f(x) := 0 \quad \text{if } x < 0$$ Justify that $f \in \mathcal{C}^1(\mathbb{R})$ and that $f$ is convex. Give the set of its minimizers.
iran-konkur 2013 Q113 View
113- If $f(x) = \text{Max}\{|2x|, |x+1|\}$, then what is the minimum value of $f(x)$?
(1) $\dfrac{1}{3}$ (2) $\dfrac{2}{3}$ (3) $\dfrac{4}{3}$ (4) $2$
iran-konkur 2013 Q121 View
121- The set of lengths of inflection points of the curve $y = x|x^2 - 4x|$ is which of the following?
(1) $\left\{\dfrac{4}{3}\right\}$ (2) $\left\{0, \dfrac{4}{3}, 4\right\}$ (3) $\left\{\dfrac{4}{3}, 4\right\}$ (4) $\left\{0, \dfrac{4}{3}\right\}$
italy-esame-di-stato 2017 Q10 View
10. Given the function:
$$f ( x ) = \left| 4 - x ^ { 2 } \right|$$
verify that it does not satisfy all the hypotheses of Rolle's theorem in the interval $[-3; 3]$ and that nevertheless there exists at least one point in the interval $[-3; 3]$ where the first derivative of $f(x)$ vanishes. Does this example contradict Rolle's theorem? Justify your answer thoroughly.
\footnotetext{Maximum duration of the examination: 6 hours. The use of scientific and/or graphing calculators is permitted provided they are not equipped with symbolic computation capability (O.M. no. 257 Art. 18 paragraph 8). The use of a bilingual dictionary (Italian – language of the country of origin) is permitted for candidates whose native language is not Italian. It is not permitted to leave the Institute before 3 hours have elapsed from the dictation of the theme. }
jee-advanced 1999 Q17 View
17. The function $f ( x ) = ( x 2 - 1 ) | x 2 - 3 x + 2 |$ is NOT differentiable at:
(A) - 1
(B) 0
(C) 1
(D) 2
jee-advanced 1999 Q29 View
29. The function $f ( x ) = \int - 1 x t$ (et-1)(t-1)(t-2)3(t-3)5dt has a local minimum at $x =$
(A) 0
(B) 1
(C) 2
(D) 3
jee-advanced 2000 Q28 View
28. Let $f ( x ) = \left\{ \begin{array} { c l l } | x | & \text { for } 0 < | x | \leq 2 \\ 1 & \text { for } & x = 0 . \end{array} \right.$
Then at $\mathrm { x } = 0 , \mathrm { f }$ has :
(A) A local maximum
(B) no local maximum
(C) a local minimum
(D) no extremum
jee-advanced 2008 Q6 View
The total number of local maxima and local minima of the function $$f ( x ) = \begin{cases} ( 2 + x ) ^ { 3 } , & - 3 < x \leq - 1 \\ x ^ { 2 / 3 } , & - 1 < x < 2 \end{cases}$$ is
(A) 0
(B) 1
(C) 2
(D) 3
jee-advanced 2014 Q54 View
Let $f : \mathbb{R} \rightarrow \mathbb{R}$ and $g : \mathbb{R} \rightarrow \mathbb{R}$ be respectively given by $f(x) = |x| + 1$ and $g(x) = x^2 + 1$. Define $h : \mathbb{R} \rightarrow \mathbb{R}$ by $$h(x) = \begin{cases} \max\{f(x), g(x)\} & \text{if } x \leq 0 \\ \min\{f(x), g(x)\} & \text{if } x > 0 \end{cases}$$ The number of points at which $h(x)$ is not differentiable is
jee-advanced 2019 Q10 View
Let $f : \mathbb { R } \rightarrow \mathbb { R }$ be given by $$f ( x ) = \left\{ \begin{aligned} x ^ { 5 } + 5 x ^ { 4 } + 10 x ^ { 3 } + 10 x ^ { 2 } + 3 x + 1 , & x < 0 \\ x ^ { 2 } - x + 1 , & 0 \leq x < 1 \\ \frac { 2 } { 3 } x ^ { 3 } - 4 x ^ { 2 } + 7 x - \frac { 8 } { 3 } , & 1 \leq x < 3 \\ ( x - 2 ) \log _ { e } ( x - 2 ) - x + \frac { 10 } { 3 } , & x \geq 3 \end{aligned} \right.$$ Then which of the following options is/are correct?
(A) $f$ is increasing on $( - \infty , 0 )$
(B) $f ^ { \prime }$ has a local maximum at $x = 1$
(C) $f$ is onto
(D) $f ^ { \prime }$ is NOT differentiable at $x = 1$
jee-main 2022 Q73 View
Let $f ( x ) = \left\{ \begin{array} { c c } x ^ { 3 } - x ^ { 2 } + 10 x - 7 , & x \leq 1 \\ - 2 x + \log _ { 2 } \left( b ^ { 2 } - 4 \right) , & x > 1 \end{array} \right.$ Then the set of all values of $b$, for which $f ( x )$ has maximum value at $x = 1$, is:
(1) $( - 6 , - 2 )$
(2) $( 2,6 )$
(3) $[ - 6 , - 2 ) \cup ( 2,6 ]$
(4) $[ - \sqrt { 6 } , - 2 ) \cup ( 2 , \sqrt { 6 } ]$
jee-main 2022 Q73 View
Let a function $f : \mathbb { R } \rightarrow \mathbb { R }$ be defined as: $f ( x ) = \begin{cases} \int _ { 0 } ^ { x } ( 5 - | t - 3 | ) d t , & x > 4 \\ x ^ { 2 } + b x , & x \leq 4 \end{cases}$ where $b \in \mathbb { R }$. If $f$ is continuous at $x = 4$, then which of the following statements is NOT true?
(1) $f$ is not differentiable at $x = 4$
(2) $f ^ { \prime } ( 3 ) + f ^ { \prime } ( 5 ) = \frac { 35 } { 4 }$
(3) $f$ is increasing in $\left( - \infty , \frac { 1 } { 8 } \right) \cup ( 8 , \infty )$
(4) $f$ has a local minima at $x = \frac { 1 } { 8 }$
jee-main 2025 Q4 View
The sum of all local minimum values of the function
$$f ( x ) = \left\{ \begin{array} { l r } 1 - 2 x , & x < - 1 \\ \frac { 1 } { 3 } ( 7 + 2 | x | ) , & - 1 \leq x \leq 2 \\ \frac { 11 } { 18 } ( x - 4 ) ( x - 5 ) , & x > 2 \end{array} \right.$$
is
(1) $\frac { 157 } { 72 }$
(2) $\frac { 131 } { 72 }$
(3) $\frac { 171 } { 72 }$
(4) $\frac { 167 } { 72 }$