(1-а) •(1+а +а2) +a3

To simplify the given expression, we will expand the terms using the distributive property.

(1 - a) • (1 + a + a^2) + a^3

Expanding the expression:

= 1(1 + a + a^2) - a(1 + a + a^2) + a^3 = 1 + a + a^2 - a - a^2 - a^3 + a^3 = 1 - a

Therefore, the simplified form of the expression is 1 - a.