ACT Preparation / Unit 11 ACT 1024 short lesson, about 20 seconds
The Factor Theorem
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The idea
By the factor theorem, x − c is a factor of a polynomial exactly when f(c) = 0, so factors and zeros match.
In practice
f(x) = x³ − 7x + 6: f(1) = 0, so x − 1 is a factor.
Where people slip
A nonzero value rules the factor out: f(3) = 12, so x − 3 is not a factor.
Your place on the trail
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