The roster form of the given sets are:
(i) A = {1, 3, 5, 7, 9, 11, 13, 15, 17, 19}.
(ii) B = {1, 2, 3, 4, 5, 6, 7}.
(iii) C = {27, 64}.
(iv) D = {-1, 0, 1}.
The roster form of any set is the set with all elements of the set written in the set.
In the question, we are asked to represent the known sets in the roster form.
(i) A=The set of all odd natural numbers less than 20.
The set of all natural numbers, that is numbers after 1.
Odd numbers are numbers of the form 2n - 1.
Thus, the roster form is: A = {1, 3, 5, 7, 9, 11, 13, 15, 17, 19}.
Going similarly to the others, we will get:
(ii) B={y: y = n, n ∈ N, n ≤7}
Roster form is, B = {1, 2, 3, 4, 5, 6, 7}.
(iii) C = {x: x is a perfect cube, 8 < x < 125}
Roster form is, C = {27, 64}.
(iv) D= {x: x ∈ Z, -2 < x < 2}.
The roster form is, D = {-1, 0, 1}.
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means the one on the left is the same as, or less than the one on the right. The one on the right is 21. N would be 3 because 7 x 3 = 21. Therefore 7n is the same as 21. 7 x 3 = 21. N=3.