Respuesta :

Step-by-step explanation:

Use grouping.

f(x) = x⁴ + 2x³ − 9x² + 18x

f(x) = x³ (x + 2) − 9x (x + 2)

f(x) = (x³ − 9x) (x + 2)

f(x) = x (x² − 9) (x + 2)

f(x) = x (x − 3) (x + 3) (x + 2)