【单选题】Scientists in general believe that croplands, forests, and grasslands will supply enough raw materials, food, and fuel to guarantee further economic growth in the years to come.
【简答题】(文)设F 1 、F 2 分别为椭圆C: x 2 m 2 + y 2 n 2 =1 (m>0,n>0且m≠n)的两个焦点. (1)若椭圆C上的点A(1, 3 2 )到两个焦点的距离之和等于4,求椭圆C的方程. (2)如果点P是(1)中所得椭圆上的任意一点,且 P F 1 ? P F 2 =0 ,求△PF 1 F 2 的面积. (3)若椭圆C具有如下性质:设M、N是椭圆C上关于原点对称的两点,点Q是...