Is it possible to solve this problem for "i" given b and n as constants > 1:
(i + 1)n(bi-1) = -1
i is the rate of a loan of term n with beginning balance b
That works out to an (n+1)th degree polynomial equation in i. Even given specific numbers, there are no general methods for solving polynomials of degree higher than 4. There are various numerical methods you could use but they would require giving specific values to b and n.