Once a king got two nice falcons(猎鹰)from his son. He had never seen such beautiful falcons before. He loved them so much and he ordered the best falconer to train them to fly.
After several months, the king came to see how the training was going on. He found that one falcon had already been able to fly high in the sky, while the other was staying on the branch(树枝) of a tree quietly, just keeping still.
The king called all his falcons together and ordered them to try every way they could to make the other falcon fly. But none of them succeeded. One day, while the king was taking a walk in the forest, an idea came to his mind. Maybe someone who knew the natural environment well could solve this problem. He spent for a farmer who lived in the forest into his palace to train it at once.
The next morning, the king saw the other falcon flying above in the sky freely. “ it is unbelievable !” shouted the king. How could you make it happen?”
The farmer replied,“It's very easy. I just cut off the branch where the falcon rested.”
It is always the same to human beings. We all have “two flying wings” in our hearts as well, but we often seem not to notice them and stay where we just for safety and comfort. We won't realize we can fly so high and freely until the “branch” we are resting on breaks.
，若
是
的一个极值点，则
的值为（ ）
