(a) a (a^{2} + a + 1) + 5 = a^{3} + a^{2} + a + 5

(i) For a = 0, a^{3} + a^{2} + a + 5 = 0 + 0 + 0 + 5 = 5

(ii) For a = 1, a^{3} + a^{2} + a + 5 = (1)^{3} + (1)^{2} + 1 + 5 = 1 + 1 + 1 + 5 = 8

(iii) For a = −1, a^{3} + a^{2 }+ a + 5 = (−1)^{3} + (−1)^{2} + (−1) + 5 = − 1 + 1 − 1 + 5 = 4