Question
I am interested in the root of the polynomial function :
$x^4+(a+b+c+d-2)x^3+(ab+ac+ad+bc+bd+cd-2b-2c-a-d)x^2 +(abc+abd+acd+bcd-ab-ac-ad-2bc-bd-cd-a-d+b+c)z+ abcd-abc-bcd-ad+bc=0$$x^4+(a+b+c+d-2)x^3+(ab+ac+ad+bc+bd+cd-2b-2c-a-d)x^2 +(abc+abd+acd+bcd-ab-ac-ad-2bc-bd-cd-a-d+b+c)x+ abcd-abc-bcd-ad+bc=0$
Under the restriction that: $0<a,b,c,d<1$.
I tried Vietas formula but don’t know how to come to a decomposition
$a_0=abcd-abc-bcd-ad+bc=x_1x_2x_3x_4$