Solving equations involving log

Hi, All

How can i solve for 'x' in following equation given values of 'N' , 'U' and 'r' using Matlab.

Answer 1

[Rick Rosson]

x   =  log (  1  +  U * (r^N - 1)  )   /  log(r);

[Masood Abbasi]

Thanks Rick

I know that its the equation we get, but how can i formulate my equation in Matlab equation solver to get solution (x) without writing all equation myself

Answer 2

[madhan ravi]

syms x r N U
eqn=(r^x-1)/(r^N-1)==U;
x=solve(eqn,x);
pretty(x) %to display in a neat manner

Answer 3

[Star Strider]

Using built-in MATLAB functions (no Toolboxes required):

U = 4.2;
N = 1.1;
r = 3.1;
fcn = @(x) ((r.^x - 1)./(r.^N -1)) - U;
x_soln = fzero(fcn, 1)

and more robustly, using the Optimization Toolbox:

x_soln = fsolve(fcn, 1)

Experiment to get the result you want.