Question

Which of the following is the roster form of the set A = {4x² - x - 5 = 0 : x ∈ I}
1. {1, -1.25}
2. {1} 
3. {-1, 1.25}
4. {-1}

Answer 1

Correct Answer - Option 4 : {-1}

Concept:

Roster form is one in which all the elements of the set are shown

Calculation

Given: A = {4x2 - x - 5 = 0 : x ∈ I}

4x2 - x - 5 = 0

⇒ (x + 1)(4x - 5) = 0

⇒ x = -1, 1.25

For set A, x ∈ I

∴ Roster form of set A = {-1}