SOLUTION: Please help I get very confused on these type of math problems. Any help is greatly appreciated. (4√5-8√2)(5√5+10√2)=

Algebra ->  Square-cubic-other-roots -> SOLUTION: Please help I get very confused on these type of math problems. Any help is greatly appreciated. (4√5-8√2)(5√5+10√2)=      Log On


   

Question 607002: Please help I get very confused on these type of math problems. Any help is greatly appreciated.
(4√5-8√2)(5√5+10√2)=
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
(4√5-8√2)(5√5+10√2)=
:
(4sqrt%285%29-8sqrt%282%29)*(5sqrt%285%29%2B10sqrt%282%29)
FOIL
First: 4sqrt%285%29%2A5sqrt%285%29 = 20(5) = 100, we have sqrt(5)*sqrt(5) so it's just 5
:
Outer: 4sqrt%285%29%2A10sqrt%282%29 = 40sqrt%2810%29
:
Inner: -8sqrt%282%29%2A5sqrt%285%29 = -40sqrt%2810%29
:
Last: -8sqrt%282%29%2A10sqrt%282%29 = -80(2) = -160
:
so we have
100 + 40sqrt%2810%29 - 40sqrt%2810%29 - 160
The middle two terms cancel out, leaving
100 - 160 = -60
:
Did this un-confuse you somewhat?