(文)已知函數(shù)y=的圖象按向量n=(b,0)平移后得到函數(shù)y=的圖象,則函數(shù)f(x)=a^x-b(a＞0且a≠1)的反函數(shù)f^-1(x)的圖象恒過定點(diǎn)

A.(2,1)               B.(1,2)                   C.(-2,1)             D.(0,2)

下面四個(gè)命題:①f(x)=+ 是函數(shù)；②函數(shù)是其定義域到值域的映射；   ③函數(shù)y=2x的圖象是一條直線；④函數(shù)y=的圖象是拋物線.其中正確的有

A.1個(gè)                          B.2個(gè)                          C.3個(gè)                          D.4個(gè)

函數(shù)y=的圖象是平面上到兩定點(diǎn)距離之差的絕對(duì)值等于定長的點(diǎn)的軌跡,則這兩個(gè)定點(diǎn)間的距離為(    )

A.8                        B.4

C.4                        D.2

函數(shù)y=的圖象是平面上到兩定點(diǎn)距離之差的絕對(duì)值等于定長的點(diǎn)的軌跡,則這兩個(gè)定點(diǎn)間的距離為

A.8                                                                 B.4

C.4                                                                 D.2

函數(shù)y=的圖象是平面上到兩定點(diǎn)距離之差的絕對(duì)值等于定長的點(diǎn)的軌跡,則這兩個(gè)定點(diǎn)間的距離為(    )

A.8                        B.4

C.4                        D.2