Help with characteristic equation

[standout]

Hi, I don't know what I am doing wrong. This is from a control systems textbook:

Where am I mistaken? 

 

 

[Country Boy]

The general solution to the quadratic equation, $ax^2+ bx+ c= 0$ is NOT $\frac{-b}{2a}\pm\sqrt{b^2- 4ac}$.  It is $\frac{-b\pm \sqrt{b^2- 4ac}}{2a}$.

Edited February 7, 2018 by Country Boy

[standout]

7 hours ago, HallsofIvy said:

The general solution to the quadratic equation, $ax^2+ bx+ c= 0$ is NOT $\frac{-b}{2a}\pm\sqrt{b^2- 4ac}$.  It is $\frac{-b\pm \sqrt{b^2- 4ac}}{2a}$.

thanks!