JEE Advanced · Mathematics · 29. Differential Eqns
Let \(y(x)\) be the solution of the differential equation
\(x^2 \frac{d y}{d x}+x y=x^2+y^2, x>\frac{1}{e}\)
satisfying \(y(1)=0\). Then the value of \(2 \frac{(y(e))^2}{y\left(e^2\right)}\) is _____ .
- A 0.78
- B 0.47
- C 0.15
- D 0.75
Answer & Solution
Correct Answer
(D) 0.75
Step-by-step Solution
Detailed explanation
Put \(\mathrm{y}=\mathrm{vx} \Rightarrow \frac{d y}{d x}=v+x \frac{d v}{d x}\)
D.E.
\(\begin{aligned}
& \mathrm{x}^2\left(v+\mathrm{x} \frac{\mathrm{~d} v}{\mathrm{dx}}\right)+\mathrm{x}^2 v=\mathrm{x}^2\left(1+v^2\right) \\
& \Rightarrow v+x \frac{d v}{d x}+v=1+v^2 \\
& \Rightarrow x \frac{d v}{d x}=1+v^2-2 v \\
& \Rightarrow \int \frac{d v}{(v-1)^2}=\int \frac{d x}{x} \\
& \Rightarrow-\frac{1}{v-1}=\ln |x|+\mathrm{C}
\end{aligned}\)
\(\Rightarrow \frac{\mathrm{x}}{\mathrm{x}-\mathrm{y}}=\ln |x|+\mathrm{C}=\ln \mathrm{x}+\mathrm{C} \quad\left(\right.\) Since \(\left.\mathrm{x}>\frac{1}{\mathrm{e}}\right)\)
Given \(y(1)=0\)
\(\Rightarrow C=1\)
So \(\frac{x}{x-y}=\ln (e x)\)
Now \(y(e)=\frac{e}{2}\) and \(y\left(e^2\right)=\frac{2 e^2}{3}\)
\(\therefore \frac{2(y(e))^2}{y\left(e^2\right)}=\frac{2 \cdot \frac{e^2}{4}}{\frac{2 e^2}{3}}=\frac{3}{4}=0.75\)
D.E.
\(\begin{aligned}
& \mathrm{x}^2\left(v+\mathrm{x} \frac{\mathrm{~d} v}{\mathrm{dx}}\right)+\mathrm{x}^2 v=\mathrm{x}^2\left(1+v^2\right) \\
& \Rightarrow v+x \frac{d v}{d x}+v=1+v^2 \\
& \Rightarrow x \frac{d v}{d x}=1+v^2-2 v \\
& \Rightarrow \int \frac{d v}{(v-1)^2}=\int \frac{d x}{x} \\
& \Rightarrow-\frac{1}{v-1}=\ln |x|+\mathrm{C}
\end{aligned}\)
\(\Rightarrow \frac{\mathrm{x}}{\mathrm{x}-\mathrm{y}}=\ln |x|+\mathrm{C}=\ln \mathrm{x}+\mathrm{C} \quad\left(\right.\) Since \(\left.\mathrm{x}>\frac{1}{\mathrm{e}}\right)\)
Given \(y(1)=0\)
\(\Rightarrow C=1\)
So \(\frac{x}{x-y}=\ln (e x)\)
Now \(y(e)=\frac{e}{2}\) and \(y\left(e^2\right)=\frac{2 e^2}{3}\)
\(\therefore \frac{2(y(e))^2}{y\left(e^2\right)}=\frac{2 \cdot \frac{e^2}{4}}{\frac{2 e^2}{3}}=\frac{3}{4}=0.75\)
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 Mathematics
- Paragraph:
Let \(f:[0,1] \rightarrow \mathbb{R}\) (the set of all real numbers) be a function. Suppose the function \(f\) is twice differentiable, \(f(0)=f(1)=0\) and satisfies \(f^{\prime \prime}(x)-2 f^{\prime}(x)+f(x) \geq e^{x}, x \in[0,1] .\)
Question:
Which of the following is true for \(f(x)\) ?JEE Advanced 2013 Hard - Let and be the following straight lines.
and
Suppose the straight line lies in the plane containing and , and passes through the point of intersection of and . If the line bisects the acute angle between the lines and , then which of the following statements is/are TRUE?JEE Advanced 2020 Medium - A group of 9 students, \(\mathrm{s}_1, \mathrm{~s}_2, \ldots \ldots, \mathrm{s}_9\), is to be divided to from three teams \(\mathrm{X}, \mathrm{Y}\), and \(\mathrm{Z}\) of sizes 2,3 , and 4 , respectively. Suppose that \(s_1\) cannot be selected for the team \(\mathrm{X}\), and \(\mathrm{s}_2\) cannot be selected for the team Y. Then the number of ways to from such teams, isJEE Advanced 2024 Hard
- Let \(f(x)=2+\cos x\) for all real \(x\).
Statement I For each real \(t\), there exists a point \(c\) in \([t, t+\pi]\) such that \(f^{\prime}(c)=0\).
Statement II \(f(t)=f(t+2 \pi)\) for each real \(t\).JEE Advanced 2007 Easy - For nonnegative integers and , let . For positive integers and let , where for any nonnegative integer ,
. Then which of the following statements is/are TRUE?JEE Advanced 2020 Hard - In , consider the planes and Let , be a plane, different from and , which passes through the intersection of and . If the distance of the point , from , is , and the distance of a point , from , is , then which of the following relations is (are) true ?JEE Advanced 2015 Easy
More PYQs from JEE Advanced
- The structure of a peptide is given below.
If the absolute values of the net charge of the peptide at and are and respectively, then what is ?
JEE Advanced 2020 Medium - Which of the following inequalities is/are TRUE?JEE Advanced 2020 Hard
- The correct functional group \(X\) and the reagent/reaction conditions \(Y\) in the following schemes are \(\mathrm{X}-\left(\mathrm{CH}_2\right)_4-X\)
JEE Advanced 2011 Hard - A plano-convex lens is made of a material of refractive index n. When a small object is placed 30 cm away in front of the curved surface of the lens, an image of double the size of the object is produced. Due to reflection from the convex surface of the lens, another faint image is observed at a distance of 10 cm away from the lens. Which of the following statement(s) is (are) true?JEE Advanced 2016 Hard
- In a Young's double slit experiment, the separation between the two slits is \(d\) and the wavelength of the light is \(\lambda\). The intensity of light falling on slit 1 is four times the intensity of light falling on slit 2 . Choose the correct choice(s),JEE Advanced 2008 Medium
- The correct option(s) related to the extraction of iron from its ore in the blast furnace operating in the temperature range is(are)JEE Advanced 2022 Medium