How to get the positive root of the cubic a*x^3+3*b*x^2+3*c*x+d=0

How to get the positive root of the cubic a*x^3+3*b*x^2+3*c*x+d=0 where a=1,c=b+2, d=-3 and b=.1:.1:2.

If rr is the root, find rr/(rr+1) for each b.

Answer 1

[Kye Taylor]

You can try

b = .1:.1:2;
a = 1;
c = b+2;
d = -3;

posR = zeros(1,length(b));
for i = 1:length(b)
    r = roots([a,3*b(i),3*c(i),d]);
    posR(i) = r(r>0); % only one real root for the values you specified
    posR(i) = posR(i)/(posR(i)+1);
end

Answer 2

[rania saidi]

Résolution équation ax3+bx2+cx+d=0 MATLAB

Answer 3

[rania saidi]

Résolution équation a*x^3+b*x^2+c*x+d=0 a=6 ; b=1 ; c=-4; d=1 dans matlab