Question

Simplify the following expression
$(5 + \sqrt{5} )(5 - \sqrt{5} )$


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Answer 1

Step-by-step explanation:

=

${5}^{2} - { \sqrt{5} }^{2} \\ = 25 - 5 = 20$

Answer 2

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

According to identity

•°• (a+b)(a-b) =a^2-b^2

so,

$= {(5)}^{2} - {( \sqrt{5} )}^{2}$

$= 25 - 5$

$= 20$