I am trying to find formula for f[x] whose expansion in powers of x is:(adsbygoogle = window.adsbygoogle || []).push({});

x + 2^2 x^2 + 3^2 x^3 + 4^2 x^4 + ... + k^2 x^k + ...

I know that this is a variation on x/(1-x). I also know that x/(1-x)^2 yields expansion in power of x = kx^k. I cannot figure out the manipulation which would give the expansion k^2x^k.

Any help is appreciated

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# Find formula for f[x] whose expansion in powers of x is

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