Q: The sum of all the coefficients of the terms in the expansion of $(x+y+z+w)^{6}$ which contain $x$ but not $y$ is:
What I tried to do was make pairs of two terms and the expand it as a binomial expression and then again expand the binomial in the resulting series which gave me an expression with lot of unknowns and I got stuck.
Any help would be appreciated.
Thanks.
Best Answer
Hint: What happens if you evaluate your expression in $x=1,y=0,z=1,w=1$? And in $x=0,y=0,z=1,w=1$?