Fzero for functions that are never negative?

[Joza]

I felt this was important enough to give it its own thread...

Using fzero, how does one find the root of a function that is always
positive, or zero, but never negative? For instance, an absolute value: 
f(x) = abs(x - 2)

This has root = 2, but I can't give it an initial bracket [x1,x2] since
f(x2)*f(x2) >= 0.
Indeed, how could fzero even find an initial bracket?

In a particular problem I am dealing with, I must find the root of f(x) =
abs(x-9.1)^4.5 using fzero, and I am supplied with initial x values of 8.0
and 13.0.

But fzero fails if I pass these values as an initial bracket, and passing
only one of them fails also. Is it impossible to solve such functions using
fzero?



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