I examined some rules to verify that if a certain function for example f(x)=x^2+5 is a 1-1 function or not.

What I did after defining the function was as follows:

[> assume(x>0,s>0);

[> solve(f(x)=f(s),{x,s});

OR

[> solve(f(x)=f(s),{x,s}) assuming x:: positive;

They didn't give me just

s=x

at all. Thanks so much.