Answers

2014-07-14T01:41:42+08:00
Do you mean how to expand the square of a trinomial

(a + b + c)²  =    a² +b² + c² + 2ab + 2ac + 2bc
(a + b -c)²  =      a² + b² + c² + 2ac -2ac - 2bc
(a - b + c )²        a² + b² +c² - 2ab + 2ac - 2bc  
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