已知正比例函数y=（3m﹣1）$x^{m^2-2}$的图象经过第一、三象限，求m的值．

在猜想弹性势能可能与哪几个物理量有关的时候，有人猜想弹性势能可能与弹簧的劲度系数k、弹簧的伸长量x有关，但究竟是与x的一次方，还是x的二次方，还是x的三次方有关呢?请完成下列练习以帮助思考。

①若弹性势能E_p∝kx，由于劲度系数k的单位是N/m，弹簧伸长量x的单位是m，则kx的单位是____。

②若弹性势能Ep∝kx²，由于劲度系数k的单位是N/m，弹簧伸长量x的单位是m，则kx²的单位是____。

③若弹性势能Ep∝kx³，由于劲度系数k的单位是N/m，弹簧伸长量x的单位是m，则kx³的单位是____。

从①②③中对单位的计算，你可以得到的启示：____。

    A man was worried his wife wasn't hearing as well as she used to and he thought she might need some hearing aid (助听). Not quite sure how to1her, he called the family doctor to discuss the problem. The doctor told him there was a simple test the husband could do to give the doctor a better2of her hearing loss.

    "Here's what you do," said the doctor. "Stand about 40 feet away from her, and in a3conversational speaking tone (音调) see if she hears you. If not, go to 30 feet, then 20 feet, and so on4you get a reply."

    That evening, the wife was in the5, and he was in the yard. He said to himself, "I'm about 40 feet away, and let me see what will happen." Then in a usual tone he asked,"Honey, what's for dinner?"

    No6.

    So the husband moved closer to the kitchen, about 30 feet from his wife and asked,"Honey, what's for dinner?"

    7no reply.

    Next he moved into the dining room where he was about 20 feet from his wife and8, "Honey, what's for dinner?"

    Again he got no reply. He walked up to the kitchen door, about 10 feet away. "Honey,what's for dinner?" Again there was no reply.

    So he9right up behind her. "Honey, what's for dinner?"

    "Chicken! David, for the10time I've said that."