Sagot :
Answer:
1. x-r is a factor of P(x) if and only if the remainder R of P(x) is divided by (x-r) is equals to 0.
2. By the remainder theorem, R=0 if and only if (x-r) is a factor of P(x).
3. Thus, (x-3) is a factor of P(x) if and only if P(r)=0