(1-а) •(1+а +а2) +a3

To simplify the expression (1-а) •(1+а +а^2) +a^3, we can first distribute the terms:

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

Now, simplify the expression by combining like terms:

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

Therefore, the simplified expression is 1 - 2a.