Question

Q.Write the following sets in the roster form.
(i) A = {x | x is a positive integer less than 10 and 2x – 1 is an odd number}
(ii) C = {x : x2 + 7x – 8 = 0, x ∈ R}

Class 11 Chapter 1
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Answer 1

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(i) x is a positive integer according to question and is less than 10.

Now, while substituting positive values less than 10 in 2x - 1, the answers we may get are : 1, 3, 5, 7, 9, 11, 13, 15, 17. All the results we get are odd.

So, the set in roaster form will be :-

A = {1, 3, 5, 7, 9, 11, 13, 15, 17}

(ii) x² + 7x - 8 = 0, Solving the Given quadratic equation.

x² + 8x - x + 8 = 0

x (x + 8) -1 (x + 8) = 0

(x - 1) (x + 8) =0

x = 1 or -8

So, both of them are Real numbers.

Hence, C = {1, -8}