Given a polynomial f(x), if (x - 1) is a factor, what else must be true?
f(0) = 1, f(1) = 0, f(-1) = 0, f(0) = -1.

Solution:

Given, a polynomial f(x)

(x - 1) is a factor.

Then, for x = 1 the polynomial must be equal to zero.

f(1) = 0

Therefore, f(1) = 0 is true.

Example: 

Given, a polynomial f(x) = x³ +x²+x+1

(x + 1) is a factor.

Then, for x = -1 the polynomial must be equal to zero.

Let us verify it.

f(-1) = -(1)³ +(-1)²⁺(-1) +1

= -1 +1 -1 +1

f(-1) = 0

Therefore, f(-1) = 0 is true.

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Given a polynomial f(x), if (x - 1) is a factor, what else must be true?
f(0) = 1, f(1) = 0, f(-1) = 0, f(0) = -1.

Summary:

Given a polynomial f(x), if (x - 1) is a factor, f(1)=0 must be true.