
Couple binomial Things
First, can some tell me if I did this right, and if not, tell me what I did wrong.
expand (x+4y)^5
I got: x^5 + 20x^4y + 26x^3y^2 + 74x^2y^3 + 261xy^4 + 1024y^5
Second, I've forgotten the formulas for exponential growth and decay, If someone could provide those I'd greatly appreciate it.

using the binomial formula:

ummm
I used Pascal's triangle, I was wondering if my numerical coefficients are correct mostly, what you said went over my head, thanks for trying to help me anyways :) and still looking for exponential growth and decay formulas, they have something to do with halflife I think.
