k1=1/2;
p3_k1 = [+1, 2*(2*k1-1), 8*k1+1, 4*k1]
roots(p3_k1)
k2=(1+sqrt(2))/4;
p3_k2 = [+1, 2*(2*k2-1), 8*k2+1, 4*k2]

roots(p3_k2)