Further, in
the chapter on Integral Calculus, we discussed  how to find
a function f whose derivative is the function g, which may
also be formulated as follows:
For a given function g, find a function f such that
dy
dx  = g(x), where y = f(x) (1)
An equation of the form (1) is known as a differential
equation A formal definition will be given later These equations arise in a variety of applications, may it be in Physics, Chemistry,
Biology, Anthropology, Geology,  Economics etc