The differential equation of the family of all non-horizontal lines in a plane is

Answer

`(d^(2)y)/(dx^(2))=0`

Explanation

Alll such lines are given by `y=mx+c`.
Here, we have two effective constants m and c. So, it is required to differentiate twice.
`y=mx+c`
`therefore (dy)/(dx)=m`
or `(d^(2)y)/(dx^(2))=0`