Find the general solution of
y^{(4)}-4 y^{\prime \prime \prime}+6 y^{\prime \prime}-4 y^{\prime}+y=0Find the general solution of
y^{(4)}-4 y^{\prime \prime \prime}+6 y^{\prime \prime}-4 y^{\prime}+y=0The characteristic equation is
\lambda^{4}-4 \lambda^{3}+6 \lambda^{2}-4 \lambda+1=(\lambda-1)^{4}=0.
with the single root \lambda=1 of multiplicity 4 . Thus four linearly independent solutions are
y_{1}=e^{x}, y_{2}=x e^{x}, y_{3}=x^{2} e^{x} \text { and } y_{4}=x^{3} e^{x}.
The general solution is
y(x)=e^{x}\left(c_{1}+c_{2} x+c_{3} x^{2}+c_{4} x^{3}\right).