Question

Write the following sets in the roaster form. 

(i) A = {x | x is a positive integer less than 10 and 2x – 1 is an odd number} 

(ii) C = {x : x 2 + 7x – 8 = 0, x ∈ R}

Answer 1

(i) 2^x – 1 is always an odd number for all positive integral values of x. In particular, 2^x – 1 is an odd number for x = 1, 2, ... , 9. Thus, A = {1, 2, 3, 4, 5, 6, 7, 8, 9}. 

(ii) x² + 7x – 8 = 0 or (x + 8) (x – 1) = 0 giving x = – 8 or x = 1 

Thus, C = {– 8, 1}