Question

Find the differential equation of all streight lies in a plane

Answer 1

Step-by-step explanation:

You can neither express all lines in terms of a function y(x) nor express all lines in terms of a function x(y), since in each case there are lines that aren't described by such functions. This is a matter of the form in which you represent the functions, not of the differential equations that you impose on that form.

All lines can be represented in the form (x(s),y(s)), where s is an arc length parameter, and in this representation the differential equation for lines is d2ds2(x(s),y(s))=0.