Plotting multiple step response for multiple transfer function

Im trying to plot multiple step response in a single plot, but somehow the transfer function is always stable, by right from my analysis it should be goign unstable at K = 26.25 but somehow it is still stable in the plot. Im still new to matlab and this is my code

for K = 1:20:50

GS = tf(K,[1 8 19 12]);

step(GS)

hold on;

end

Answer 1

[Paul]

What's the basis for the assertion that GS should be unstable at K = 26.25? As you've seen, that clearly cannot be the case because the denominator of GS, i.e., the poles of GS, does not depend on K. Maybe the form of GS is not correct, or at least doesn't represent what you think it represents.