function inversion



maxima-bounces at math.utexas.edu wrote on 02/17/2011 11:45:56 AM:

> I defined a function giving a set of points with linearinterpol then I 
added 
> another function, which I defined with a simple formula. The resulting 
> function is still strictly rising in value, so mathematically it can be 
> inverted, so I wanted to invert the function, but I could not find an 
> operator for that anywere, I tried
> 
> simplify([y=f(x)],x), which produced some expression, but not what I 
needed 

Instead of simplify, maybe you need to use solve; try something like

 (%i8) solve(y = 5 * x + 7,x);
 (%o8) [x=(y-7)/5]

Thus the inverse of f(x) = 5 x + 7 is g(y) = (y-7)/5.

--Barton