Question

U+K=−Gm1m2/r+1/2 m1 v2,

where m1 and m2 are the masses of two objects, r is the distance between their centers, v is the velocity, and G is the universal gravitational constant.

How can you rearrange the given formula to correctly find m1?

Answer 1

fix your typos, and then just factor out m1 and you have
U+K = m1(1/2 v^2 - Gm2/r^2)
now divide to get m1 all alone

Answer 2

I think -G m1 m2 / r is correct. It is potential energy, not force, integral of 1/ r^2 from infinity to r