( ( )) ( ( )) ( ( )), ,F XYF X F XF Y X F Y F X X YR
Câu 3: (1 điểm) Tìm
f R: Rthỏa mãn:
(
( ))
(
( ))
(
( )),
,
f x
yf x
f xf y
x
f y
f x
x y
R
(
( ))
(
( ))
(
( )),
,
f x
yf x
f xf y
x
f y
f x
x y
R