A system defined by the following equations, the transfer function, \(G\left( s \right) = \frac{{Y\left( s \right)}}{{U\left( s \right)}}\) = \( \frac{{3s + 5}}{{{s^2} + 4s + 6}}\)

\(\dot x = \left[ {\begin{array}{*{20}{c}} { - 4}&{ - 1.5}\\ 4&0 \end{array}} \right]x + \left[ {\begin{array}{*{20}{c}} 2\\ 0 \end{array}} \right]u\)

y = [α β] x. Then α + β = _____