I need help!!! What should i do if i want to get out r from this function where i already have a and b. (1-(1/(1+r))^b)/r=a is there any logarithm and if there is in what library do i find it

"Lembit" <> wrote in message news:... > I need help!!! > What should i do if i want to get out r from this function where i already > have a and b. > > (1-(1/(1+r))^b)/r=a is there any logarithm and if there is in what library > do i find it I think this is correct. Check it. (1-(1/(1+r))^b)/r=a (1-(1/(1+r))^b)=a*r 1-(1/(1+r)) = (a*r)^(1/b) -1/(1+r) = (a*r)^(1/b)-1 1/(1+r) = -((a*r)^(1/b)-1) 1+r = 1/(-((a*r)^(1/b)-1)) r = 1/(-((a*r)^(1/b)-1))-1 /Fredrik

"Fredrik Wahlgren" <> wrote in message news:%... > > "Lembit" <> wrote in message > news:... > > I need help!!! > > What should i do if i want to get out r from this function where i already > > have a and b. > > > > (1-(1/(1+r))^b)/r=a is there any logarithm and if there is in what library > > do i find it > Forget my previous reply

Lembit wrote: > I need help!!! > What should i do if i want to get out r from this function where i > already have a and b. > > (1-(1/(1+r))^b)/r=a is there any logarithm and if there is in what > library do i find it I'm too lazy to attempt the algebra at the moment, but looking at it, I'd say no, there is no formula for that value - you'll have to use numerical methods to search for a suitable r for a given a and b. For example, you might use "Newton's Method" to solve this. You'll likely have to look it up in a numerical methods book or a calculus book. -cd