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Q.
8 The sum of all the coefficients of terms in the expansion of $(x+y+z+w)^4$ which contain $x$ but not $y$, is
Binomial Theorem
Solution:
Sum of coefficient of terms not having $y=3^4=81$
(putting $x = z = w = 1 $ and $y= 0$)
sum of coefficient of terms not having $y$ and $x=2^4=16 $
(putting $x=y=0$ and $z=w=1$ )
$\therefore$ sum of coefficient of terms having $x$ but not $y =81-16=65$