6. Let A= {1, 2, 3, 4, 6}. Let R be the relation on A defined by {(a, b): a, b E A, b is exactly divisible by a}. (i) Write R in roster form (ii) Find the domain of R (iii) Find the range of R. 7. Prove the following by using the principle of mathematical induction for all n = N: 32n+28n 9 is divisible by 8. 8. Prove that: (sin 3x + sin x) sin x + (cos 3x cos x) cos x = 0. 3 3 3