Question

函數(shù)y=

1

2

x+b的圖象與函數(shù)y=ax-5的圖象關(guān)于y=x對(duì)稱，則a+b的值為（　�。�

A． 9 4

B．- 9 4

C．- 9 2

D． 9 2

Answer 1

由于互為反函數(shù)的圖象關(guān)于y=x對(duì)稱，
又由函數(shù)y=

1

2

x+b的圖象與函數(shù)y=ax-5的圖象關(guān)于y=x對(duì)稱，
故函數(shù)y=

1

2

x+b與函數(shù)y=ax-5互為反函數(shù)
又由函數(shù)y=

1

2

x+b的反函數(shù)為y=2x-2b
故a=2，2b=5
故a+b=

9

2

故選D