How do you multiply $(sqrt10 + 1)(8sqrt10 +1)$ ?

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Answer 1 · 2015-06-12T16:38:11

$= color(blue)(81 +9sqrt10)$

$(sqrt10 + 1)(8sqrt10 +1)$

$=color(blue)((sqrt10 . 8sqrt10) + (sqrt(10).1)) + color(red)((1 . 8sqrt10) + (1.1))$
$= color(blue)(80 +sqrt10) + color(red)(8sqrt10 +1$

Grouping like terms:
$color(blue)(80 +1) + color(red)(sqrt10 +8sqrt10)$
$= color(blue)(81 +9sqrt10)$

How do you multiply (sqrt10 + 1)(8sqrt10 +1)(sqrt10 + 1)(8sqrt10 +1)?