Question

$(5 + \sqrt{5) (5 - \sqrt{5)} }$
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Answer 1

Answer:

20

Step-by-step explanation:

$(5 + \sqrt{5} )(5 - \sqrt{5} ) \\l et \: a = 5 \: and \: b = \sqrt{5} \\ since(a + b) (a - b) = {a}^{2} - {b}^{2} \\ = > (5 + \sqrt{5} )(5 - \sqrt{5} ) = {(5)}^{2} - ( { \sqrt{5} )}^{2} \\ = 25 - 5 = 20$