I desire to solve this:

c:12-1,23*(1+x/2)
solve(c;x)=17,512195

I get the value of x, but if I write

c:12-1,23*(1+x/3)
solve(c;x)=

I get the message "no real roots" (in this case the value of x is 26,268292)

Someone can help me to understand why?

Stefano

Stefano,

Try using the solve function with 4 arguments, where the third and fourth arguments are the lower and upper bounds respectively within which the root may be found. See screenshot below:



Graphing the function can help in choosing a suitable interval for the lower and upper bounds. Please see the following thread and wiki page for more info:
Solve not working
Solve function

BTW: An improved solve function would be a great plugin project for someone to work on. Maybe someday.

Thank you Maweilian,
before posting my question I read only this post http://en.smath.info/forum/default.aspx?g=posts&t=434, so I supposed that the need for an interval was only for non linear equation. I read carefully the posts you linked in your answer and now I understood the behaviour of solve function.
Thank you again.

Stefano