Monday 24 June 2013

Proof by induction, induction step

I am trying to prove



$$
\sum_{k=1}^n k2^{k-1} = 1+(n-1)2^n
$$



I proved the base case with $n = 1$. I am having trouble proving the induction step.




I know I need to prove for $n = n +1$ so I got



$$
\sum_{k=1}^n k2^{k-1}+(k+1)2^{(k+1)-1} = 1+[(n+1)-1]2^{n+1}
$$



suppose $n = i$



$$
1 + [(i+1)-1] 2^{i+1}

$$



I am not sure if I am on the right path and how to simplify from here onwards? Could someone point me in the right direction?

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