Q.If \(\sqrt{10} - 3 = k\), then what is the value of \(\sqrt{10} + 3\)? (a) \(2k\) (b) \(\cfrac{1}{k}\) (c) \(\cfrac{1}{2k}\) (d) \(-\cfrac{1}{k}\)
Answer: B
\(\sqrt{10} - 3 = k\) i.e., \(k = \sqrt{10} - 3\) i.e., \(k(\sqrt{10} + 3) = (\sqrt{10} - 3)(\sqrt{10} + 3)\) i.e., \(k(\sqrt{10} + 3) = (\sqrt{10})^2 - (3)^2\) i.e., \(k(\sqrt{10} + 3) = 10 - 9\) i.e., \(k(\sqrt{10} + 3) = 1\) i.e., \(\sqrt{10} + 3 = \cfrac{1}{k}\)
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