Câu 20. Phát biểu nào sau đây là đúng: A.
2 2
x y x y   
B.
 
2 2 2
x y x y   

C. x y   0 thì
x  0
hoặc
y  0 D.
x y   0
thì
xy  0

Three baby penguins and their father were sitting on an iceberg 0.50.50, point, 5 meters above the surface of the water. the father dove down 4.74.74, point, 7 meters from the iceberg into the water to catch dinner for his kids. what is the father penguin's position relative to the surface of the water?

Which expression is equivalent to -5(3x - 6/7)

Two cars which are 40 miles apart start moving simultaneously in the same direction with constant speeds. if the speed of the car which is behind is 56 mph and the speed of the other car is 48 mph, how many hours will it take for the car which is behind to catch up the car ahead of it?