Second Order Linear

Second Order Linear Ordinary Differential Equations follow the general form

Theorem I

Let , , and be continuous and on the open interval then there exists a unique solution for the Initial Value Problem, and

Example

Theorem II: Superposition Principle

Also called the superposition principle for homogenous equations
If and are two solutions of a homogenous equation

Then is also a solution

Theorem III: Wronskian

If and are two solutions of a homogenous equation and

Then is the general solution

Wronskian

Let and be two solutions of a homogenous equation, the Wronskian of the equation can be given as

If then and are linearly dependent
If then and are linearly independent

Theorem II vs Theorem III

While both theorems give a similar form, theorem III gives the general solution while theorem II only gives a single solution

Example

Theorem IV

Let and be two solutions of a homogenous equation

If the Wronskian of the solutions at is not zero

For the initial condition: and
There exists a unique choice of and such that

Example

Proof for the condition that

Theorems Compared

Theorem II Theorem III Theorem IV
Type of Equation Homogeneous
Homogeneous
Homogeneous
Initial Condition - -
Solutions


Wronskian -
Conclusion A Solution
General Solution
Arbitrary Constants
,