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?_______
双曲线的一条渐近线与直线垂直,则这双曲线的离心率为___。
椭圆的焦点、,点为其上的动点,当∠为钝角时,点横坐标的取值范围是 。
双曲线的渐近线方程为,焦距为,这双曲线的方程为_______________。
抛物线的准线方程为_____.
若曲线表示双曲线,则的取值范围是。