Second order differential equations of the form

E I y=0, representing an equation for the

deflected profile y of a pin-ended uniform strut

of length l subjected to a load P. E is Young’s modulus and I is the second moment of area.

IfD represents d dx

andD2 represents d2

dx2 then the above

equation may be stated as (aD2 + bD+ c)y=0. This equation is said to be in ‘D-operator’ form.