Thank you Joe! & Robert! and Axel! In fact, I need this in Matlab. I thought I would be able to solve the problem once I can do it in Maple since I did: function ph=phi(k,v) solve('1+(x/.2)*(log(x/.2)-1)=.5*v-sqrt(k)*x'); ph=subs(ans); and enter phi(.98, .4) at the command line. this gave the 1st ans I noticed the solution before subs(ans) is the same that Maple gives so I thought I would be able to solve the problem once I can do it in Maple. I tried using the maple command in Matlab but it's not working out...