Could someone please solve this (and explain how to approach these sort of questions):
Suppose a polynomial is given by P(x)= (x-a)(x-b)(x-c)-(b+c)(c+a)(a+b).
a.) Show that x=a+b+c is a zero of P(x)
B.) Hence, or otherwise, factorise the polynomial P(x)= (x-2)(x+3)(x+1)-4.
Answer for a wasn't...