The coefficient of x2012 in the expansion of (1-x)2008 (1+x+x2 )2007 is equal to .
Answer
0
Solution
(1-x)2008 (1+x+x2 )2007=(1-x) [(1-x) (1+x+x2 ) ]2007=(1-x) (1-x3 )2007
(1-x3 )2007 has only powers x3r the product has only powers x3r and x3r+1
2012=3 670+2 is of the form 3r+2
no x2012 term; coefficient =0
Answer: 0