If W = {x : x is a natural number and x² = 9}, what is the roster form of W?
Answer and explanation
Correct answer: W = {3}
First solve the condition x² = 9. The two integer solutions are x = 3 and x = −3. The second condition restricts x to natural numbers; under the standard school convention, −3 is not natural, while 3 is natural. Therefore the set contains only one element, and its roster form is W = {3}. Option B is correct; option A ignores the natural-number restriction.
Frequently asked questions
What is the correct answer to this question?
W = {3}
Why is this the correct answer?
First solve the condition x² = 9. The two integer solutions are x = 3 and x = −3. The second condition restricts x to natural numbers; under the standard school convention, −3 is not natural, while 3 is natural. Therefore the set contains only one element, and its roster form is W = {3}. Option B is correct; option A ignores the natural-number restriction.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Common Questions. Topic: General chapter practice.
