Solved
with inputs for f and g the equation f-g is wrongly calculated because strangely the +4 isn't changed into -4 in a basic substraction.
online: https://www.geogebra.org/m/yjzre4ay
The same problem 
with inputs for f and g the equation f-g is wrongly calculated because strangely the +4 isn't changed into -4 in a basic substraction.
online: https://www.geogebra.org/m/yjzre4ay
typing f(x)-g(x)=0 is OK
muchas gracias. Writing brackets indeed prevents the error.
Graphically f - g shows the line x = 1 while in the Algebra it gives x = -3/5.
The same solution in the Algebra as in the Graphics could be expected in any case.
Fixed for v659
Comments have been locked on this page!