Need some help with this expansion

[buoyant walrus]

Hello math pro, i need some help with this expansion that i dont understand how to simplify

[crimson frigate]

@buoyant walrus Hint: Use the binomial formula, then identify the coefficient of x^i

[keen frigate]

have you done sth ?

[keen frigate]

try with the binomial theorem

[buoyant walrus]

I already did that, i do get something similar yet its different

theres a (n-1)! factor in the denominator

[crimson frigate]

@buoyant walrus

Now finish this by simplifying the quotient of factorials!

[stray hinge]

.close