Question

15• (√a +√ b) (√a - √b) is *

•a + b
•a-b
•2√a
•2√b​

Answer 1

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$• \: a - b \\ \\ using \: identity \\ (a + b)(a - b) = a {}^{2} - b {}^{2} \\ \\ putting \: value \\ ( \sqrt{a} + \sqrt{b} )( \sqrt{a} - \sqrt{b} ) = \\ \\ \sqrt{a {}^{2} } - \sqrt{b { }^{2} } \\ square \: will \: be \: cancelled \: \\ \: by \: under \: root \\ \\ therefore \\ \\ answer = a - b$