Question

[Nguyễn Minh Hằng]

1.The Ford car left Hanoi for Nghe An and the Audi car left Nghe An for Hanoi at the same time. The ratio of their speeds (the Ford car to the Audi car) was 4:3. The Ford car decreased its speed by 25% and the Audi car increased its speed by 25% after they had passed each other. When the Ford car reached Nghe An, the Audi car was still 20 km away from Hanoi. The distance between Hanoi and Nghe An is .... km

2.The smallest value of A= \(\frac{x-y}{x^{4}+y^{4}+6}\) is.....