def resistor_parallel(resistors: list[float]) -> float:

    first_sum = 0.00
    index = 0
    for resistor in resistors:
        if resistor <= 0:
            raise ValueError(f"Resistor at index {index} has a negative or zero value!")
        first_sum += 1 / float(resistor)
        index += 1
    return 1 / first_sum