方程 x² = 3x的根是 （    ）

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    People with an impulsive personality refer to those who tend to do things without considering the possible dangers or problems first. According to a new study by researchers at the University of Georgia, such people may be more likely to have food addiction. The study found that people exhibiting impulsive behavior weren't necessarily overweight, but impulsiveness was related to a direct relationship with food, and therefore, less healthy weight.

    Food addiction has been compared to addictive drug use. Studies have linked the dopamine (多巴胺) release that occurs after tasting delicious food to the dopamine release that happens when people consume other addictive substances.

    Impulsive behavior involves several personality traits (特点). Two of these traits, known as negative urgency and lack of perseverance, were particularly associated with food addiction and high BMI (身体质量指数) during the study.

    Negative urgency is characterized by the tendency to behave impulsively when experiencing negative emotions. Some people might drink alcohol or take drugs. For others, it could mean eating to feel better. Lack of perseverance is when a person has a hard time finishing hard or boring tasks. People with a lack of perseverance might have difficulty attempting to change addictive eating behavior, which could also cause obesity.

    “Impulsiveness might be one reason why some people eat in an addictive way despite motivation to lose weight,” said Dr. Ashley Gearhardt, a clinical psychologist. He was involved in developing the Yale Food Addiction Scale in aid of those people. “We are theorizing that if food addiction is really a thing, then our measure, the Yale Food Addiction Scale, should be related to helping control impulsive action,” said Gearhardt.

    Clinical psychologist Dr. James MacKillop, whose lab was conducting the study, believes that therapies used to treat addictive drug behavior could help people who suffer from addictive eating habits.

    “Most of the programs for weight loss at this point focus on the most obvious things, which are clearly diet and exercise,” MacKillop said. “It seems that managing strong desires to eat would naturally fit in with the skills a person would need to eat healthily.”

    In 1973, I was teaching elementary school. Each day,27kids1“The Thinking Laboratory.” That was the 2 students voted for after deciding that “Room 104” was too3.

    Freddy was an average4,but not an average person .He had the rare balance of fun and compassion（同情）.He would5 the loudest over fun and be the saddest over anyone's6.

    Before the school year7,I gave the kids a special 8, T-shirts with the words “Verbs Are Your9” on them. I had advised the kids that while verbs（动词）may seem dull ,most of the10 things they do throughout their lives will be verbs.

    Through the years, I'd run into former students who would provide 11 on old classmates. I learned that Freddy did several jobs after his 12 from high school and remained the same 13 person I met forty years before .Once, while working overnight at a store, he let a homeless man 14in his truck. Another time ,he 15a friend money to buy a house .

    Just last year, I was16 a workshop when someone knocked at the classroom door. A woman17 the interruption and handed me an envelope. I stopped teaching and 18 it up. Inside were the “Verbs” shirt and a 19 from Freddy's mother. “Freddy passed away on Thanksgiving. He wanted you to have this.”

    I told the story  to the class. As sad as it was, I couldn't help smiling. Although Freddy was taken from us, we all20something from Freddy.

对生态平衡不利的人类活动是（    ）