题干

已知函数y=f(x)在区间[a,b]上的图象是连续不断的一条曲线,有下列说法:

①若f(a)•f(b)>0,则函数y=f(x)在区间(a,b)上没有零点;

②若f(a)•f(b)>0,则函数y=f(x)在区间(a,b)上可能有零点;

③若f(a)•f(b)<0,则函数y=f(x)在区间(a,b)上没有零点;

④若f(a)•f(b)<0,则函数y=f(x)在区间(a,b)上至少有一个零点;

其中正确说法的序号是____(把所有正确说法的序号都填上).

上一题 下一题 0.0难度 选择题 更新时间:2018-04-25 07:28:35

答案(点此获取答案解析)

②④

同类题5

阅读理解

    Children like to imagine they are someone else in a game. As a parent you might never guess how it can benefit your child. It helps your child:

Develop Social Skills

    As children play pretend games, they explore relationships between family members, friends and coworkers and learn more about how people interact. Playing doctor, they imagine how physicians care for their patients. Imaginative play helps of a game or to lose a pet, they are better able to help those in need. They become more willing to play fair, to share, and to cooperate.

Build Self-confidence

    Children have very little control over their lives. Imagining oneself as a builder of skyscrapers or a super hero defending the planet is inspiring to children. It helps them develop confidence in their abilities and their potential.

Promote Intellectual Growth

    Using imagination is the beginning of abstract thought. Children who can see a king's castle in a mound of sand or a delicious dinner in a mud pie are learning to think symbolically(象征性地). This skill is important in school where a child will have to learn that numbers symbolize groups of objects, letters symbolize sounds, and so on.

Practice Language Skills

    Kids who pretend with their friends do a lot of talking. This helps increase their vocabulary, improve sentence structure and develop communication skills.

Get Rid of Fears

    Pretending can help children get rid of their fears and worries. When children role-play the big, bad monsters under the bed, they gain a sense of control over him and he doesn't seem quite so big or so bad.