Question

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

• A. 81
• B. 16
• C. 175
• D. 65

Answer 1

Answer: (D)

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 $y=81-16=65$