Answer
a³ - a² - 3a + 6
Explanation
The equation requires you to subtract the two expressions.
(a³ - 2a) - (a² + a - 6)
In such an expression we subtract the like term only.
(a³ - 2a) - (a² + a - 6) = a³ - 2a - a² - a + 6
= a³ - a² -2a - a + 6
= a³ - a² - 3a + 6
