D'Alembert Formula

Power Series - Radius of Convergence

Method of Frobenius

Discrimant classification
b^2 - ac <, = , >

Reduction of order

Variation of Parameters
y''+p1(x)y'+p0(x)y=q(x)

2nd Order Linear Homogeneous ODE w. Constant coefficients
y''+ay'+by=0

Legendre's Equation

Bessel's Equations

Laguerre's Equation

Hermite's Equation