What does this code output for x_data = [0, 1, 2], y_data = [1, 3, 7], x = 1.5?

def newton_backward(x_data, y_data, x):

    h = x_data[1] - x_data[0]

    s = (x - x_data[-1]) / h

    result = y_data[-1] + s*(y_data[-1] - y_data[-2])

    return result