单选题下列四个级数中发散的是A．B．C．D．

单选题已知都发散，则

单选题设，其中bn=2∫01f(x)sinnnxdx，则等于A．B．C．D．

单选题设在x=-2处条件收敛，则在处

单选题若二次型为正定二次型，则λ的取值范围是______

单选题Self-esteem is the collection of beliefs or feelings we have about ourselves, our "self-perceptions. " How we define ourselves influences our motivations, attitudes, and behaviors and affects our emotional adjustment. Patterns of self-esteem start very early in life. For example, a toddler who reaches a milestone experiences a sense of accomplishment that bolsters self-esteem. Learning to roll over after dozens of unsuccessful attempts teaches a baby a "can-do" attitude. The concept of success following persistence starts early. As kids try, fail, try again, fail again, and then finally succeed, they develop ideas about their own capabilities. At the same time, they're creating a self-concept based on interactions with other people. This is why parental involvement is important to helping kids form accurate, healthy self-perceptions. Self-esteem fluctuates as kids grow. It's frequently changed and fine-tuned, because it is affected by a child's experiences and new perceptions. So it helps to be aware of the signs of both healthy and unhealthy self-esteem. Kids with low self-esteem may not want to try new things, and may frequently speak negatively about themselves. They tend to be overly critical of and easily disappointed in themselves. Kids with low self-esteem see temporary setbacks as permanent, intolerable conditions, and a sense of pessimism predominates. Kids with healthy self-esteem tend to enjoy interacting with others. They're comfortable in social settings and enjoy group activities as well as independent pursuits. When challenges arise, they can work toward finding solutions and voice discontent without belittling themselves or others. How can a parent help to foster healthy self-esteem in a child? Kids who don't feel safe or are abused at home will suffer immensely from low self-esteem. A child who is exposed to parents who fight and argue repeatedly may become depressed and withdrawn. Also watch for signs of abuse by others, problems in school, trouble with peers, and other factors that may affect kids' self-esteem. Deal with these issues sensitively but swiftly. And always remember to respect your kids. If you suspect your child has low self-esteem, consider doing something about it. Family and child counselors can work to uncover underlying issues that prevent a child from feeling good about him or herself. Therapy can help kids learn to view themselves and the world positively. When kids see themselves in a more realistic light, they can accept who they truly are. With a little help, every child can develop healthy self-esteem for a happier, more fulfilling life.

单选题设X，Y是相互独立的随机变量，它们的分布函数分别是FX(x)，FY(y)，则Z=max(X，Y)的分布函数是______．

单选题设A为n(n≥2)阶方阵，A * 为A的伴随矩阵，若对任一n维列向量α，均有A*α=0，则齐次线性方程组Ax=0的基础解系所含解向量的个数k必定满足______

单选题设A为m阶可逆矩阵，B为n阶可逆矩阵，|A|=a，|B|=b，则等于()

单选题由曲线y=(0≤x≤π)与x轴围成的平面图形绕x轴旋转而成的旋转体体积为______A．．B．．C．．D．．

单选题直线的夹角为()