# Another Summation (Part 2)

Algebra Level 4

$\large \displaystyle \sum_{m=1}^{\infty} \dfrac{m^2}{2^m}$

The summation above is equal to $$\dfrac{a}{b} + c$$, where $$a,b,c$$ are integers, with $$a$$ and $$b$$ positive and $$\text{gcd}(a,b) = 1$$, and $$0 \leq c <1$$. Find $$a+b-c$$.

P.S. Don't get tricked!

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