Answer:
(x - 2)(x - 21)
Explanation:
x² - 23x + 42
consider the factors of the constant term (+ 42) which sum to give the coefficient of the x- term (- 23 )
the factors are - 2 and - 21 , since
- 2 × - 21 = + 42 and - 2 - 21 = - 23
use these factors to split the x- term
x² - 2x - 21x + 42 ( factor the first/second and third/fourth terms )
= x(x - 2) - 21(x - 2) ← factor out (x - 2) from each term
= (x - 2)(x - 21) ← in factored form