If U={x: x is a natural number and x²=16}, what is its roster form?
Answer and explanation
Correct answer: U={4}
The governing concept is solving a defining condition while respecting the stated domain. Algebraically, x²=16 gives x=4 or x=-4. However, U is restricted to natural numbers; 4 is natural, whereas -4 is not. Consequently the only member is 4, so U={4}. Option A ignores the domain restriction, C keeps the invalid root, and D confuses x² with x.
Frequently asked questions
What is the correct answer to this question?
U={4}
Why is this the correct answer?
The governing concept is solving a defining condition while respecting the stated domain. Algebraically, x²=16 gives x=4 or x=-4. However, U is restricted to natural numbers; 4 is natural, whereas -4 is not. Consequently the only member is 4, so U={4}. Option A ignores the domain restriction, C keeps the invalid root, and D confuses x² with x.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Number Systems.
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