Form the differential equation of the family of circles having centers on the x-axis and radius unity.
Form the differential equation of the family of circles having centers on the x-axis and radius unity.

Equation of the family of circles having centers on the x-axis and radius unity can be represented by (x-a)^{2}+(y)^{2}=1, where a is an arbitrary constants.
(x-a)^{2}+y^{2}=1(1)
Differentiating the above equation with respect to x on both sides, we have,
\begin{array}{l} 2(x-a)+2(y) \frac{d y}{d x}=0 \\ x-a+y \frac{d y}{d x}=0 \\ a=x+y \frac{d y}{d x} \end{array}
Substituting the value of \mathrm{a} in equation (1)
\begin{array}{l} \left(x-x-y \frac{d y}{d x}\right)^{2}+y^{2}=1 \\ \left(y \frac{d y}{d x}\right)^{2}+y^{2}=1 \end{array}
This is the required differential equation.