- #1

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## Homework Statement:

- prove that the mean position after a given number of steps is the starting position

## Relevant Equations:

- random walk

Hi

I tried like this.

##σ^2=<(λ_1+λ_2+,,,+λ_i)^2>=<λ_1^2>+<λ_2^2>+,,,<λ_i^2>##

And I know ##σ^2=Σ_in_iλ_i^2##from equation (4-12) (so this is cheat ).

So I know also ##<λ_i^2>=n_iλ_i^2##, But why??

I know if I take ##λ=1 ,σ^2=n##,But I don't understand ##λ≠1## version.

Sorry my bad english.

Please help me!