Question #7ea37

2 Answers
Mar 30, 2017

frac{(2n+1)!}{(2n-1)!}(2n+1)!(2n1)!

Expand the factorial in the numerator:

=frac{(2n+1)(2n)color(blue)((2n-1)!)}{color(blue)((2n-1)!)}(2n+1)(2n)(2n1)!(2n1)!

=(2n+1)(2n)=(2n+1)(2n)

=2(2n+1)(n)=2(2n+1)(n)

Mar 30, 2017

((2n+1)!)/((2n-1)!) = color(green)(4n^2+2n)(2n+1)!(2n1)!=4n2+2n

Explanation:

((2n+1)!)/((2n-1)!)(2n+1)!(2n1)!

color(white)("XXX")=((2n+1) * (2n) * cancel((2n-1)) * cancel((2n-2)) * cancel((2n-3)) * ... * cancel(2) * cancel(1))/(cancel((2n-1)) * cancel((2n-2)) * cancel((2n-3)) * ... cancel(2) * cancel(1))

color(white)("XXX")=(2n+1) * (2n)

color(white)("XXX")=4n^2+2n