The correct interpretation of the initial value in the function \( f(x) = 35x + 50 \) is:
The initial value of 50 represents the one-time membership fee.
In this function, \( x \) represents the number of months, $35 is the monthly fee, and $50 is the one-time membership fee. Therefore, when \( x = 0 \) (indicating the beginning, or at the time of joining), the cost \( f(0) = 35(0) + 50 = 50 \), which is the one-time fee Hector pays to join the gym.