1. I this from my hw solution.(adsbygoogle = window.adsbygoogle || []).push({});

(1-t/s)^n = exp(-t/s)

as n goes to infinity

I don't understand. I checked the exponential power series. It should be :

exp(x) = summation (x^n / n!)

n=0 to infinity

How come it could be a exponential function ?

2. another is that why

<t> = integral from 0 to infinity (t*P(t) dt) ?

average t

P(t)dt = probability that an electron has no colission till time t *

probability that it has a collision between time t

probablitiy has no collision is exp(-t/s)

t+dt = exp(-t/s) *dt/s

Thanks a lot !

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# Homework Help: Power series / exponential

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