BITSAT 2014
- Exam
- BITSAT
- Year
- 2014
- Subject
- Mathematics
- Chapter
- Differential Equations
BITSAT 2014 · Mathematics · Differential Equations
Solution of differential equation x^ 2 =1+((x)/(y))^ -1 (d y)/(d...
Solution of differential equation x^{2}=1+\left(\frac{x}{y}\right)^{-1} \frac{d y}{d x}+\frac{\left(\frac{x}{y}\right)^{-2}\left(\frac{d y}{d x}\right)^{2}}{2 !}+\frac{\left(\frac{x}{y}\right)^{-3}\left(\frac{d y}{d x}\right)^{3}}{3 !}+\ldots \text{ is }
Options
- A
- B
- C
- D
Correct answer
A.
Step-by-step solution
x^{2}=e^{\left(\frac{x}{y}\right)^{-1}\left(\frac{d y}{d x}\right)} \Rightarrow x^{2}=e^{\left(\frac{y}{x}\right)\left(\frac{d y}{d x}\right)}\Rightarrow \ln x^{2}=\frac{y}{x} \frac{d y}{d x}\int x \ln x^{2} d x=\int y d yx^{2}=t \Rightarrow 2 x d x=d t \therefore \frac{1}{2} \int \ln t d t=\frac{y^{2}}{2}C+t \ln t-t=y^{2}y^{2}=x^{2}\left(\ln x^{2}-1\right)+C