If A = {x ∈ ℝ : x² = x + 2} and B = {-1, 2}, choose the correct option.
Answer and explanation
Correct answer: A = B
Rearrange the equation as x² - x - 2 = 0. Factoring gives (x - 2)(x + 1) = 0, so x = 2 or x = -1. Both values are real and therefore A = {-1, 2}. Since B contains exactly these same elements, A = B. The order in which elements are written does not affect a set.
Frequently asked questions
What is the correct answer to this question?
A = B
Why is this the correct answer?
Rearrange the equation as x² - x - 2 = 0. Factoring gives (x - 2)(x + 1) = 0, so x = 2 or x = -1. Both values are real and therefore A = {-1, 2}. Since B contains exactly these same elements, A = B. The order in which elements are written does not affect a set.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: The Empty Set, Finite and Infinite Sets, Equal Sets.