How do I calculate galactic mass as a function of r? I know it is supposed to be proportional to r. I've seen,(adsbygoogle = window.adsbygoogle || []).push({});

M(r)=v^{2}r/G

And also I've seen

M(r)=vrc^{2}/G

Which if any is right?

And what do I use for v?

Thanks so much for your help!

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# Galactic mass proportional to r

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