Answer:
(fog)(a) = a³ - 3a² + 4a - 2
= (a - 1)×(a² - 2a + 2)
Explanation:
Given :
g(a) = a -1
f(a)= a³ +a
…………………………
(fog)(a) = f(g(a)))
= g(a)³ + g(a)
= (a - 1)³ + (a - 1)
= (a³ - 3a² + 3a - 1) + (a - 1)
= a³ - 3a² + 3a - 1 + a - 1
= a³ - 3a² + 3a + a - 1 - 1
= a³ - 3a² + 4a - 2
Second method :
(fog)(a) = f(g(a)))
= f(a - 1)
= (a - 1)³ + (a - 1)
= (a - 1)×[(a - 1)² + 1]
= (a - 1)×[a² - 2a + 1 + 1]
= (a - 1)×(a² - 2a + 2)