A.4x+2y=5                                           

B.4x－2y=5

C.x+2y=5                                             

D.x－2y=5

　A.与y=e^x的图象关于y轴对称

B.与y=e^x的图象关于坐标原点对称

C.与y=－e^－x的图象关于y轴对称

D.与y=e^－x的图象关于坐标原点对称

A.75°                      

B.60°                

C.45°               

D.30°

A.－                    

B.                 

C.－                   

D.

A.（x+1）²+y²=1                                 

B.x²+y²=1

C.x²+（y+1）²=1                                 

D.x²+（y－1）²=1

A.y=3x－4                                           

B.y=－3x+2

C.y=－4x+3                                                

D.y=4x－5

A.y=－5（x≠0）                               

B.y=x+5（x∈R）

C.y=+5（x≠0）                                

D.y=x－5（x∈R）

A.{x|x<－2}             

B.{x|x>3}          

C.{x|－1<x<2}  

D.{x|2<x<3}

（Ⅰ）求四棱锥P—ABCD的体积;

（Ⅱ）证明PA⊥BD.