.
1. This statement, as it presented in the post, might be TRUE and MIGHT be FALSE,
DEPENDING on the polynomial f(x).
For example, if f(x) =
, then (x-3) is the factor of f(x), but f(-3) =
=
= 36 is not zero.
From the other side, if f(x) = (x-3)*(x+3), then (x-3) is the factor of f(x), and f(-3) = (3-(-3))*(3+(-3)) = 0.
2. But, if I modify the statement in this way:
Determine whether the statement is true or false.
If x - 3 is a factor of a polynomial f(x), then f(3) = 0
then this MODIFIED statement is TRUE.
It follows from the "Remainder theorem".
On "Remainder theorem" see the lesson
- Divisibility of polynomial f(x) by binomial (x-a). The Remainder theorem
in this site.