5e^(-5t) - 4e^(-8t) = 1

how to solve for t by hand? Do I take ln both sides or wat?

just looking at the coefficients, set t = 0 and you get 5 - 4 = 1

This post was edited by carteblanche on Apr 5 2016 09:48pm

yea but another answer is also t = .2115

This equation is equivalent to a 8th power polynomial equation.
Power over 4 cannot be generally solved algebraically.

All you can do is estimate an approximate value of the other solution.

how come power over 4 cant be solved algebraically?

there's no general formula (unlike powers 0 to 4), but some can be solved.

see Abel–Ruffini theorem:

https://en.wikipedia.org/wiki/Abel%E2%80%93Ruffini_theorem