How do you multiply $(7+sqrt(5b))(7–sqrt(5b))$ ?

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Answer 1 · 2015-06-18T07:56:04

$= color(blue)(49 - 5b$

This is of the form :
$color(blue)((a+b)(a-b) = a^2 - b^2$
So ,
$(7+sqrt(5b))(7–sqrt(5b)) = 7^2 - sqrt((5b))^2$

$= color(blue)(49 - 5b$

How do you multiply (7+sqrt(5b))(7–sqrt(5b))(7+sqrt(5b))(7–sqrt(5b))?