单选题与直线2x+3y一6=0关于点(1，一1)对称的直线是( )．

单选题设

单选题设函数f(x)=arctanx．若函数f(x)=xf'(ξ)，则_______.

单选题如下图，AB为半圆O的直径，C为半圆上一点，且弧AC为半圆的，设扇形AOC、三角形COB、弓形BMC的面积分别为S1、S2、S3，则下列结论正确的是A.S1最大B.S2最大C.S3最大D.S1=S3E.以上答案均不正确

单选题某校教师、职工与学生人数之比为3:0.5:100，若全校共有学生3000人，则教师有( )． (A) 70 (B) 80 (C) 90 (D) 100

单选题有n(n∈N)件不同的产品排在一排，若其中A、B两件产品排在一起的不同排法有48种，则n=( )．

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

单选题曲线y=x(x-1)(2-x)与X轴所围图形的面积可表示为()。A．B．C．D．

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 A child who is exposed to parents who fight and argue repeatedly may become depressed and withdrawn.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.