During the day, you spend a lot of time running, jumping, laughing, eating, and talking. You use up a lot of energy(能量), and by the end of the day you're tired. Sleep gives your body a chance to rest.

    But your brain (大脑) and body are not completely at rest during sleep. While you sleep, your mind may think of the things that happened during the day. It keeps the important things in mind as memories(记忆). It also thinks about things you were worrying about, and you may wake up with answers to some of your problems.

    You also grow while you sleep. The thing called "human growth hormone (荷尔蒙)" in the body helps you grow during sleep. This growth hormone also helps the body to repair itself.

    Sleep helps your body to conserve energy too. You use up a lot of energy during your daily activities. But when you sleep, your body temperature falls, and your "metabolism" (新陈代谢) slows down. You are still using some energy, but much less than when you are awake and active.

    Have you ever stayed up past your bedtime? Did you have difficulty getting up the next morning? Maybe you had problems seeing clearly or you cannot think clearly. That was your body's way of saying, "I need sleep!" A lack ( 缺乏) of sleep can stop your body and mind from working correctly.

    Have you ever complained why life is so tiring? Does the sky sometimes seem dark to you? Are your studies sometimes not successful? Well, friends, cheer up and smile all the time. If you see the world with your warm heart, you will find the whole world smiles to you.

    While in school, sometimes you are tired of your lessons, but have you ever noticed the happy smile on your teacher's face when you did a good job?

    One day it is fine. Just before you want to go out, it suddenly starts to rain. Maybe you would feel very sad and start complaining about the weather. But dear friends, why don't you sit down and listen to the concert that the nature offers you? And with the timely rain, crops in the fields will grow better and better and farmers will have a good harvest.

    Although everyone wants to succeed in what he tries to do, sometimes failure can't be avoided. I think failure is not terrible, and the terrible thing is what we are afraid of it and give up hope. When we face failure, we must be confident in ourselves, draw a useful lesson from it and try our best to finish what we have decided to do. As a popular saying goes, "Failure is the mother of success."

    Attitude decided everything. With an optimistic(乐观) attitude life is easy and pleasant. Let's smile whatever we meet and the whole world will smile to us.

解方程：（3x﹣1）²=（x+1）²