# Zeroes

In general it is hard to determine the zeroes of functions exactly. However, they can be approximated numerically. The function has three zeroes on the whole real line.
The first zero is on the interval [-2,-1], and the signs of the function values and are different. Use the command `fzero`:
```>> fzero(@f,[-2,-1])

ans =
-1.2780

>> fzero(@f(x),[-2,-1])

ans =
-1.2780
```
So it is possible to use either `f' or `f(x)'.
```>> f(ans)

ans =
-4.4409e-016
```
You can see from the last output that MATLAB has found an approximation for the zero.

Remark: When `fzero` does not find a zero of a function , this does not mean the function does not have a zero. When the wrong interval is selected, the function is discontinuous or does not cross , no zero can be found, although it may exist. This can be the case, for example, when searching for a zero of . Note that in this case the zero of the function is identical to its minimum.

Esteur 2010-03-22