Form the differential equation of the family of hyperbolas having foci on the x-axis and centers at the origin.
Form the differential equation of the family of hyperbolas having foci on the x-axis and centers at the origin.

Equation of the family of an ellipse having foci on the y-axis and centers at the origin can be represented by \frac{x^{2}}{a^{2}}-\frac{y^{2}}{b^{2}}=1 ......(1)
Differentiating the above equation with respect to \mathrm{x} on both sides, we have,
\begin{array}{l} \frac{2 x}{a^{2}}-\frac{2 y}{b^{2}} \frac{d y}{d x}=0 \\ \frac{x}{a^{2}}-\frac{y}{b^{2}} \frac{d y}{d x}=0 \\ \frac{y}{b^{2}} \frac{d y}{d x}=\frac{x}{a^{2}} \\ \frac{y}{x} \frac{d y}{d x}=\frac{b^{2}}{a^{2}} \end{array}
Again differentiating the above equation with respect to x on both sides, we have,
\begin{array}{l} \frac{y}{x} \frac{d^{2} y}{d x^{2}}+\frac{d y}{d x}\left(\frac{\frac{d y}{d x} x-y \frac{d x}{d x}}{x^{2}}\right)=0 \\ x y \frac{d^{2} y}{d x^{2}}+\frac{d y}{d x}\left(\frac{d y}{d x} x-y \frac{d x}{d x}\right)=0 \end{array}
Rearranging the above equation
x y \frac{d^{2} y}{d x^{2}}+x\left(\frac{d y}{d x}\right)^{2}-y \frac{d y}{d x}=0
This is the required differential equation.