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+//caption:value_of_K_of_characterstics_eq
+//example 7.5.7.(b)
+//page 207
+s=%s;
+syms K s1;
+CH=s^3+10*s^2+18*s+K
+s=s1-1;
+CH=eval(CH);
+CH=simple(CH);
+disp('=0',CH,"characterstics_eq,CH=");
+c0=coeffs(CH,'s1',0);
+c1=coeffs(CH,'s1',1);
+c2=coeffs(CH,'s1',2);
+c3=coeffs(CH,'s1',3);
+b=[c0 c1 c2 c3]
+n=4;
+routh=[b([4,2]);b([3,1])];
+routh=[routh;-det(routh)/routh(2,1),0]
+t=routh(2:3,1:2)
+routh=[routh;-det(t)/t(2,1),0]
+disp(routh,"routh=")
+disp("for given system to be stable:");
+disp("((-(K-16))/7)>0 and K-9>0");
+disp("which gives:");
+disp("9<K<16");