8 chapters · H.K. Dass Engineering Mathematics §3.9–3.11
A DE is an equation relating an unknown function and its derivatives. Solutions are functions, not numbers.
DEs are classified by type (ODE/PDE), order, degree, and linearity.
n arbitrary constants → differentiate n times → eliminate constants → DE of order n.
Rearrange so all y terms go left, all x terms go right, then integrate both sides.
A DE is homogeneous if f(x,y) depends only on y/x. Substitute v = y/x to convert to separable.
Standard form: + P(x)y = Q(x). Multiply by integrating factor = .
Bernoulli form: + Py = Q. Substitute z = to linearize.
A DE M dx + N dy = 0 is exact if = . Solution found by direct integration.