Which option is the value of (\sqrt{2}\times(\sqrt{18}-\sqrt{8}))?
Answer and explanation
Correct answer: (2)
The governing concept is simplifying each surd by removing perfect-square factors and then multiplying. We have \sqrt{18}=\sqrt{9\cdot2}=3\sqrt{2} and \sqrt{8}=\sqrt{4 aimes2}=2\sqrt{2}. Therefore the bracket becomes 3\sqrt{2}-2\sqrt{2}=\sqrt{2}. Multiplying by the outside factor gives \sqrt{2}\cdot\sqrt{2}=2, because \sqrt{a}\sqrt{a}=a for a non-negative a. Thus option A is correct. Option D is the unsimplified product, while B and C arise from incorrect multiplication or failure to subtract like surd terms correctly. The result is rational even though the original expression contains irrational factors.
Frequently asked questions
What is the correct answer to this question?
(2)
Why is this the correct answer?
The governing concept is simplifying each surd by removing perfect-square factors and then multiplying. We have \sqrt{18}=\sqrt{9\cdot2}=3\sqrt{2} and \sqrt{8}=\sqrt{4 aimes2}=2\sqrt{2}. Therefore the bracket becomes 3\sqrt{2}-2\sqrt{2}=\sqrt{2}. Multiplying by the outside factor gives \sqrt{2}\cdot\sqrt{2}=2, because \sqrt{a}\sqrt{a}=a for a non-negative a. Thus option A is correct. Option D is the unsimplified product, while B and C arise from incorrect multiplication or failure to subtract like surd terms correctly. The result is rational even though the original expression contains irrational factors.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Polynomials. Topic: Irrational numbers and real numbers.
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