Step 1:

$y=mx+\large\frac{a}{m}$ where m is the parameter

$\large\frac{dy}{dx}$$=m $ -----(ii)

Step 2:

Substitute for m from (ii) in (i)

$\therefore y= x \large\frac{dy}{dx}+ \large\frac{a}{\Large\frac{dy}{dx}}$

(ie) $x \bigg( \large\frac{dy}{dx}\bigg)^2$$-y \large\frac{dy}{dx}$$+a =0$

It is the required D.E