To find the vertex of the function \( f(x) = |x - \frac{4}{7}| \), we can analyze the expression inside the absolute value.
The vertex of the absolute value function \( |x - a| \) is located at the point \( (a, 0) \). In this case, \( a = \frac{4}{7} \).
Therefore, the vertex of the function \( f(x) = |x - \frac{4}{7}| \) is at the point \( \left(\frac{4}{7}, 0\right) \).
So the correct answer is: b. \((\frac{4}{7}, 0)\).