Question

What is the ninth term in the binomial expansion of (x-2y)^13

Answer 1

You just use the equation p(x)=n!/(x-n)!x!

Answer 2

`T_(9)=329472x^(5)y^8`

Explanation:

`(x-2y)^(13)`

`T_(r+1)=nCr x^(n-r) y^r`

x is the first term in the given parenthesis and y is the second tern

r= 8, r+1=9 because we need to find 9th term

x is x and y is 2y. n is the exponent 13. plug in all the values

`T_(8+1)=13C8 x^(13-8) (2y)^8`

`T_(8+1)=13C8 x^(5) (2y)^8`

nCr=

`T_(8+1)=1287x^(5) 256y^8`

`T_(9)=329472x^(5)y^8`