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

1 Answer
Don't Memorise
Jun 12, 2015

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

Explanation:

#(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)#

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