Answer:
(x - 20)(x - 1)
Explanation:
Given
x² - 21x + 20
Consider the factors of the constant term (+ 20) which sum to give the coefficient of the x- term (- 21)
The factors are - 20 and - 1 , since
- 20 × - 1 = + 20 and - 20 - 1 = - 21 , thus
x² - 21x + 20 = (x - 20)(x - 1) ← in factored form