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

Jun 18, 2015

 = color(blue)(49 - 5b

#### Explanation:

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