Question:
The coefficient of $x$ in the expansion of $(x+3)^{3}$ is
(a) 1
(b) 9
(c) 18
(d) 27
Solution:
(d) Now, (x + 3)3 = x3 + 33 + 3x (3)(x + 3)
[using identity, (a + b)3 = a3 + b3 + 3ab (a + b)]
= x3 + 27 + 9x (x + 3)
= x3 +27 + 9x2+27x Hence, the coefficient of x in (x + 3)3 is 27.