same here .
4 Answers
Hari Shankar
·Apr 30 '12 at 5:52
P(x) = xf(x) -abc is a cubic with roots a,b,c and hence is equivalent to
x3−x(a+b+c)+x2(ab+bc+ca)−abc (bearing in mind that the constant term on both sides is -abc)
so that
Its easily seen that f(a+b+c)=ab+bc+ca