If W = {x : x ∈ Z, x² = 9}, what is the roster form of W?
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Answer and explanation
Correct answer: W = {-3, 3}
To solve x² = 9, take both square roots of 9, giving x = 3 or x = -3. Both values are integers and both satisfy the equation: 3² = 9 and (-3)² = 9. Therefore the set must contain both solutions, not just one of them and not 9 itself. Hence the roster form is {-3, 3}, option C.
Frequently asked questions
What is the correct answer to this question?
W = {-3, 3}
Why is this the correct answer?
To solve x² = 9, take both square roots of 9, giving x = 3 or x = -3. Both values are integers and both satisfy the equation: 3² = 9 and (-3)² = 9. Therefore the set must contain both solutions, not just one of them and not 9 itself. Hence the roster form is {-3, 3}, option C.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Sets and their representations.
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