2.2.4.4 ✓ Mathematica. Time used: 0.015 (sec). Leaf size: 20

ode=D[x[t],{t,2}]-5*D[x[t],t]+6*x[t]==0; 
ic={}; 
DSolve[{ode,ic},x[t],t,IncludeSingularSolutions->True]
 

\begin{align*} x(t)&\to e^{2 t} \left (c_2 e^t+c_1\right ) \end{align*}