MHT CET · Maths · Functions
Let \(\mathrm{f}(x)=\mathrm{e}^x-x\) and \(\mathrm{g}(x)=x^2-x, \forall x \in \mathrm{R}\), then the set of all \(x \in \mathrm{R}\), where the function \(\mathrm{h}(x)=(\mathrm{fog})(x)\) is increasing is
- A \(\left[0, \frac{1}{2}\right] \cup[1, \infty)\)
- B \(\left[-1,-\frac{1}{2}\right] \cup\left[\frac{1}{2}, \infty\right)\)
- C \([0, \infty)\)
- D \(\left[-\frac{1}{2}, 0\right] \cup[1, \infty)\)
Answer & Solution
Correct Answer
(A) \(\left[0, \frac{1}{2}\right] \cup[1, \infty)\)
Step-by-step Solution
Detailed explanation
\(\begin{aligned}
& \mathrm{h}(x)=(\mathrm{fog})(x) \\
& \Rightarrow \mathrm{h}(x)=\mathrm{f}\left(x^2-x\right) \\
& \Rightarrow \mathrm{h}(x)=\mathrm{e}^{x^2-x}-x^2+x \\
& \therefore \quad \mathrm{h}^{\prime}(x)=\mathrm{e}^{x^2-x}(2 x-1)-2 x+1 \\
& \Rightarrow \mathrm{h}^{\prime}(x)=\left(\mathrm{e}^{x^2-x}-1\right)(2 x-1)
\end{aligned}\)
For function \(\mathrm{h}(x)\) to be increasing,
\(\begin{aligned}
& \mathrm{h}^{\prime}(x) \geq 0 \\
& \Rightarrow\left(\mathrm{e}^{x^2-x}-1\right)(2 x-1) \geq 0 \\
& \Rightarrow x \in\left[0, \frac{1}{2}\right] \cup[1, \infty)
\end{aligned}\)
\(\begin{array}{c|c|c|c}
\mathrm{h}^{\prime}- & + & - & + \\
\hline & & & \\
0 & \frac{1}{2} & 1
\end{array}\)
& \mathrm{h}(x)=(\mathrm{fog})(x) \\
& \Rightarrow \mathrm{h}(x)=\mathrm{f}\left(x^2-x\right) \\
& \Rightarrow \mathrm{h}(x)=\mathrm{e}^{x^2-x}-x^2+x \\
& \therefore \quad \mathrm{h}^{\prime}(x)=\mathrm{e}^{x^2-x}(2 x-1)-2 x+1 \\
& \Rightarrow \mathrm{h}^{\prime}(x)=\left(\mathrm{e}^{x^2-x}-1\right)(2 x-1)
\end{aligned}\)
For function \(\mathrm{h}(x)\) to be increasing,
\(\begin{aligned}
& \mathrm{h}^{\prime}(x) \geq 0 \\
& \Rightarrow\left(\mathrm{e}^{x^2-x}-1\right)(2 x-1) \geq 0 \\
& \Rightarrow x \in\left[0, \frac{1}{2}\right] \cup[1, \infty)
\end{aligned}\)
\(\begin{array}{c|c|c|c}
\mathrm{h}^{\prime}- & + & - & + \\
\hline & & & \\
0 & \frac{1}{2} & 1
\end{array}\)
See the Complete Solution
Get step-by-step explanations for this and 2.5 Lakh+ more JEE, NEET & CET questions.
- Unlock all solutions
- Practice the full chapter
- Track accuracy across PYQs
4.8 rated on Google Play · 14,000+ reviews
More questions from Maths
- The combined equation of a pair of lines passing through the origin and inclined at \(60^{\circ}\) and \(30^{\circ}\) respectively with \(\mathrm{x}\)-axis isMHT CET 2021 Easy
- If the area of the parallelogram with \(\bar{a}\) and \(\bar{b}\) as two adjacent sides is 16 sq. units, then the area of the parallelogram having \(3 \bar{a}+2 \bar{b}\) and \(\overline{\mathrm{a}}+3 \overline{\mathrm{b}}\) as two adjacent sides (in sq. units) isMHT CET 2023 Easy
- \(\frac{1^{2}}{2}+\frac{1^{2}+2^{2}}{3}+\frac{1^{2}+2^{2}+3^{2}}{4}+\frac{1^{2}+2^{2}+3^{2}+4^{2}}{5}+\ldots \ldots \ldots \ldots\) upto 8 terms \(=\)MHT CET 2020 Medium
- Let \(\bar{A}\) be a vector parallel to line of intersection of planes \(P_1\) and \(P_2\) through origin. \(P_1\) is parallel to the vectors \(2 \hat{j}+3 \hat{k}\) and \(4 \hat{j}-3 \hat{k}\) and \(P_2\) is parallel to \(\hat{\mathrm{j}}-\hat{\mathrm{k}}\) and \(3 \hat{\mathrm{i}}+3 \hat{\mathrm{j}}\), then the angle between \(\bar{A}\) and \(2 \hat{i}+\hat{j}-2 \hat{k}\) isMHT CET 2023 Medium
- If \((a,-2 a), a>0\) is the midpoint of a line segment intercepted between the co-ordinate axes, then the equation of the line isMHT CET 2020 Easy
- The abscissae of two points \(\mathrm{A}\) and \(\mathrm{B}\) are the roots of the equation \(x^2+2 a x-b^2=0\) and their ordinates are roots of the equation \(y^2+2 \mathrm{p} y-\mathrm{q}^2=0\). Then the equation of the circle with \(\mathrm{AB}\) as diameter is given byMHT CET 2023 Easy
More PYQs from MHT CET
- Lithium crystallises into body centered cubic structure. What is the radius of lithium if edge length of it's unit cell is \(351 \mathrm{pm}\) ?MHT CET 2020 Easy
- If \(\mathrm{A}=\left[\begin{array}{cc}2 & -2 \\ 4 & 3\end{array}\right]\), then \(\mathrm{A}^{-1}=\)MHT CET 2024 Easy
- A coil of wire of radius ' \(r\) ' has 600 turns and a self-inductance of 108 mH . The self-inductance of a coil with same radius and 500 turns isMHT CET 2025 Easy
- In LCR series circuit, \(\mathrm{R}=18 \Omega\) and impedance \(33 \Omega\). An r.m.s. voltage of 220 V is applied across the circuit. The true power consumed in a.c. circuit isMHT CET 2025 Medium
- If \(A=\left[\begin{array}{ll}2 & 3 \\ 1 & 2\end{array}\right], B=\left[\begin{array}{ll}1 & 0 \\ 3 & 1\end{array}\right]\), then \((A B)^{-1}=\)MHT CET 2020 Easy
- Dissolution of \(1.5 \mathrm{~g}\) of a non-volatile solute (mol. wt. \(=60\) ) in \(250 \mathrm{~g}\) of a solvent reduces its freezing point by \(0.01{ }^{\circ} \mathrm{C}\). Find the molal depression constant of the solvent.MHT CET 2010 Medium