Find the general solution of the differential equation: $e^{\frac{dy}{dx}} = x^2$.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → $y = 2x(\log x - 1) + C$ ##
Given differential equation is
$e^{\frac{dy}{dx}} = x^2$
Taking log both sides, we get
$\frac{dy}{dx} \log_e e = 2 \log x$
$\Rightarrow \frac{dy}{dx} = 2 \log x \quad [∵\log_e e = 1]$
$\Rightarrow dy = 2 \log x \, dx$
On integrating both sides, we get
$\int dy = 2 \int \log x \, dx$
$\Rightarrow y = 2 \int 1 \cdot \log x \, dx$
$\Rightarrow y = 2 \left[ \log x \int 1 dx - \int \left( \frac{d}{dx}(\log x) \int 1 dx \right) dx \right]$
[Using integration by parts]
$\Rightarrow y = 2 \left[ \log x(x) - \int \frac{1}{x}(x) dx \right]$
$\Rightarrow y = 2[x \log x - x] + C$
$\Rightarrow y = 2x(\log x - 1) + C$