How do you simplify $(6+sqrt 7)(6-sqrt 7)$ ?

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Answer 1 · 2016-02-13T17:58:54

$=color(blue)(29$

$(6+sqrt7)(6-sqrt7)$

The above expression is of the form
$color(blue)((a+b)(a-b) = a^2 - b^2$

$color(blue)(a=6, b=sqrt7$

So,
$(6+sqrt7)(6-sqrt7) = color(blue)(6^2 - (sqrt7)^2$

$=36-7$

$=29$

How do you simplify (6+sqrt 7)(6-sqrt 7)(6+sqrt 7)(6-sqrt 7)?