The differential equation
y''' - 5y'' + 7y' - 3y = 0
has characteristic equation
r ³ - 5r ² + 7r - 3 = (r - 3) (r - 1)² = 0
with roots at r = 3 and r = 1 (with multiplicity 2), so that the characteristic solution to the DE is
y = C₁ exp(3x) + C₂ exp(x) + C₃ x exp(x)
