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?_______
已知向量,且,则实数____________.
(几何证明选讲选做题)如图,点都在圆O上,过点C的切线交AB的延长线于点D,若,,,则线段AC的长为__________.
(坐标系与参数方程选做题)已知直线的参数方程为(为参数),圆C的参数方程为(为参数).若直线与圆C有公共点,则实数a的取值范围是__________.
是平面内不共线的三点,点P在该平面内且有,现将一粒黄豆随机撒在△内,则这粒黄豆落在△内的概率为__________.
已知,使不等式恒成立,则实数的取值范围是__________.