Question

Write down and simplify:
The 12th term of ${(2x-1)}^{13}$.

Answer 1

We know that the $r^{th}$ term in expansion of $(a+x{)}^n$ is given by ${}^n{C}_{r-1}{a}^{n+1-r}{x}^{r-1}$

$\therefore$ the ${12}^{th}$ term in the expansion of $(2x-1{)}^{13}$ is ${}^{13}{C}_{11}\left(2x{)}^2\right(-1{)}^{11}=-312x^2$