题干

已知{an}为等差数列,a1+a3+a5=105,a2+a4+a6=99,则数列{an}的公差d=(   )

A:﹣2

B:﹣1

C:2

D:1

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A

同类题2

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    Emily and her boyfriend had just had a fight. She felt alone and hopeless. Then she went into the kitchen and grabbed what she needed before going back up to her room quietly. She switched on the TV and started eating…and eating…for hours, until it was all gone.

     What Emily didn't know at the time was that she was suffering from an illness called binge-eating disorder(BED)(暴饮暴食).

    For years, Emily didn't tell anyone what she was doing. She felt ashamed, alone, and out of control. Why don't famous people confess (承认) to BED, as they do to anorexia? It's simple: There's a stigma(污名)involved. “Overeating is seen as very bad, but dieting to be skinny is seen as positive and even associated with determination," says Charles Sophy, a doctor in Beverly Hills , California.

    "Some parents or friends may look at a teen with BED and think, 'Oh, a good diet and some will-power will do the trick.' But that's not true," says Dr.Ovidio Bermudez , a baby doctor at the Eating Recovery Center in Denver. "Eating disorders are real physical and mental health issues; it's not about willpower." The focus in treating BED shouldn't be on weight, because as with all eating disorders, the behaviors with food are a symptom of something deeper.

    Like most other diseases, genetics may play a big part in who gets BED and who doesn't. If you have a close relative with an eating disorder, that means you're more likely to develop an eating disorder of your own.

    Besides, many people with BED have tried at some point or another to control it by going on a diet, but paying more attention to food doesn't help. And it might even make things worse, like it did for Carla, who's 15 now and is recovering from BED. "My parents would always tease me about my weight, so when I was 14, I went on a very restrictive diet," she says. When you can't have something, you only want it more, so every time Carla would have a bite of something that wasn't allowed on her strict diet. She would quickly lose control and binge (狂欢).

同类题4

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    ⑤从相反的事物有同一性、既对立又统一这个前提出发,明确思维的多向性,这是开阔思路,克服直线式、习惯性思维方式的有效途径。