French error when solving an equation

[towe]

Hey there. The oddities continue.

I was trying to solve the following equation for x:
1/sqrt(x) = 1.74- 2*log((2k/d)+(18.6/(r*sqrt(x))))
When I use specific values for k, d and r, I get the correct answer.
When attempting to solve it to an x=f(k,d,r) I get an error:
"Impossible d'isoler, Error: Valeur Argument Incorrecte"
Again, the Android app produces the same result.
Why can't the Prime do that, and why the hell does it give me errors in French?