Question

Write down and simplify:
The 4th term of ${(x-5)}^{13}$

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 fourth term in expansion of $(x-5{)}^{13}$ is ${}^{13}{C}_3{x}^{10}(-5{)}^3=-35750x^{10}$