胶体具有稳定性的原因是胶核表面带有()电荷。
A.异种
B.同种
C.正
D.负
参考答案:B
已知函数f(x)=x3+ax2+bx+a2(a、b∈R).
(1)当a=0,b=-3时,求函数f(x)在[-1,3]上的最大值;
(2)若函数f(x)在x=1处有极值10,求f(x)的解析式;
(3)当a=-2时,若函数f(x)在[2,+∞)上是单调增函数,求b的取值范围.
I am sorry to say that our food is almost______. We cannot survive if there is no one to help us.
A.by the end
B.at an end
C.in the end
D.at the end