问题
选择题
若lgx-lgy=2a,则
|
答案
∵lgx-lgy=2a,
∴lg
-lgx 2
=y 2
lg1 2
-x 2
lg1 2
=y 2
(lg1 2
-lgx 2
)y 2
=
lg1 2
=x y
(lgx-lgy)=1 2
•2a=a;1 2
故答案为C.
若lgx-lgy=2a,则
|
∵lgx-lgy=2a,
∴lg
-lgx 2
=y 2
lg1 2
-x 2
lg1 2
=y 2
(lg1 2
-lgx 2
)y 2
=
lg1 2
=x y
(lgx-lgy)=1 2
•2a=a;1 2
故答案为C.