$\frac{d^{2} y}{dx^{2}} = \left ( \frac{1}{x^{2}} \right )$ হলে y এর মান নিচের কোনটি ?  

$\begin{array}{l}\text { } \frac{\mathrm{d}^{2} \mathrm{y}}{\mathrm{dx}^{2}}=\frac{1}{\mathrm{x}^{2}} \\ \Rightarrow \int \frac{\mathrm{d}^{2} \mathrm{y}}{\mathrm{dx}^{2}} \mathrm{dx}=\int \frac{1}{\mathrm{x}^{2}} \mathrm{dx} \\ \Rightarrow \frac{\mathrm{dy}}{\mathrm{dx}}=-\frac{1}{\mathrm{x}}+\mathrm{c}_{1} \\ \Rightarrow \int \frac{\mathrm{dy}}{\mathrm{dx}} \mathrm{dx}=-\ln \mathrm{x}+\mathrm{c}_{1} \mathrm{x}+\mathrm{c} \\ \therefore \mathrm{y}=-\ln \mathrm{x}+\mathrm{c}_{1} \mathrm{x}+\mathrm{c}\end{array}$