Following the Symbolic evaluation documentation, I am trying to solve the equation: $y'(x) = a*y(x), \quad y(0)=1$ where I later fix a via FindRoot, requiring that $y(2) = 2$:
ftest[unknown_?NumberQ] := First[y[2] /. NDSolve[{y'[x] == unknown*y[x], y[0] == 1}, y, {x, 0, 4}]]
FindRoot[ftest[k] - 2, {k, 0, 4}]
This works well, but for some reason, replacing the "k" by "x" inside the Findroot outputs errors? I tried opening a new notebook and/or using Clear, but that did not solve the problem. Why does Mathematica treat x differently?