Prove that the function f given by `f(x) = | x - 1|, x in R` is not differentiable at `x = 1`

Explanation

To prove that the function \( f(x) = |x - 1| \) is not differentiable at \( x = 1 \), we will follow these steps:

### Step 1: Understand the function
The function \( f(x) = |x - 1| \) can be expressed in piecewise form:
\[
f(x) =
\begin{cases}
x - 1 & \text{if } x \geq 1 \\
...