Finding coefficients of a polynomial from roots

I have roots of a third order system. Now i need a function to get co-efficients of the polynomial for those roots. Thanks in advance

Answer 1

[Roger Stafford]

If r1, r2, and r3 are the roots, then a polynomial with those roots is:

 p(x) = (x-r1)*(x-r2)*(x-r3) = x^3-(r1+r2+r3)*x^2+(r2*r3+r3*r1+r1*r2)*x-r1*r2*r3