Find result sometimes has wrong sign

Please provide a worksheet as the image does not show all the variables.

Mike

Andrew Kelly wrote: I'm using a Given ... Find solve block in a function. When I call the function with an argument, sometimes the result has a positive sign, sometimes negative.  Mathematically it is correct, but I can't figure out why it's giving sign changes, and I only want positive results. The seeded guess value is positive.  If I seed the guess value to high to try to sneak in to the solution from the high side, the function fails frequently. I tried adding an inequality inside the solve block (R_guess>0 in) to try to force a positive result.  The function fails all the time. Looking for suggestions to get only a positive result from the Given ... Find function.

Mike has asked for your sheet.  Some of the questions that jump out:

      In the first line, what is R2?

      In the second line, what is Ereduced?

      What value do you have for scriterion?

At first look, a(R,P) is a cube root, so can be negative or positive, your solve block uses a (R,P) squared, so Pmax is forced positive whether R is positive or negative.