过椭圆C:的左顶点A且斜率为k的直线交椭圆C于另一个点B,且点B在x轴上的射影恰好为右焦点F,若<k<,则椭圆的离心率的取值范围是 。
函数的定义域是
A class collects $50 to buy flowers for a classmate who is in the hospital. Roses cost $3 each, and carnations cost $2 each. No other flowers are to be used. How many different bouquets could be purchased for exactly $50?_______
若a>0,a1,F(x)为偶函数,则G(x)=F(x)·log(x+)是_______函数(填“奇”或“偶”),它的图像关于______对称。
已知f(x)=x+(a-1)x+a在区间上是增函数,则a的取值范围是______