Question

Question 18
The coefficient of x in the expansion of $(x+3{)}^3$ is

A) 1
B) 9
C) 18
D) 27

Answer 1

$(x+3{)}^3=x^3+3^3+3x(3\left)\right(x+3)$
[Using identity $(a+b{)}^3=a^3+b^3+3ab(a+b)$]
$=x^3+27+9x(x+3)$
$=x^3+27+9x^2+27x$
Hence, the coefficient of x in $(x+3{)}^3$ is 27
So, the answer is D.