Question

Find the coefficient of $a^3{b}^{3}c$ in the expansion of $(2a+b+3c{)}^7$.

Answer 1

The binomial coefficient of $(2a{)}^3\times (b{)}^3\times (3c{)}^1=24a^3{b}^{3}c$ is given by $\frac{7!}{3!\times 3!\times 1!}=140$

So, the numerical coefficient of $a^3{b}^{3}c=24\times 140=3360$