(1-а) •(1+а +а2) +a3

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

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

= 1 + а + а^2 - а - а^2 - а^3

Now, let's add the а^3 term:

1 + а + а^2 - а - а^2 - а^3 + а^3

= 1 + а

Therefore, the simplified expression is 1 + а.