Answer:
a³ - 21a + 20
Step-by-step explanation:
expand the first pair of factors using FOIL
= (a² - 5a + 4)(a + 5)
Now, multiply each term in the first factor by each term in the second factor
= a(a² - 5a + 4) + 5(a² - 5a + 4) ← distribute parenthesis
= a³ - 5a² + 4a + 5a² - 25a + 20 ← collect like terms
= a³ - 21a + 20
