g ,
3
2
2 d y2
dy
dx
dx
⎛
⎞
+ ⎜
⎟
⎝
⎠
 = 0  is an ordinary differential equation (5)
Of course, there are differential equations involving derivatives with respect to
more than one independent variables, called partial differential equations but at this
stage we shall confine ourselves to the study of ordinary differential equations only Now onward, we will use the term ‘differential equation’ for ‘ordinary differential
equation’