According to the meaning of the question,

The unit price of oil bought by Xiaoming is

Z×﹙x+y﹚÷2Z=﹙x+y)/2

The unit price of the oil I just bought is

2H÷﹙H÷x+H÷y)=2xy÷﹙x+y)

Namely judgment

(x+y) and 2xy+y), if 2xy+y) > (x+y)/2, that is, 4xy > (x+y)?

Simplified x? +y？ Junior two math test: Xiaoming and Xiaogang go to the grain and oil store twice a month to help their mother buy oil.

Xiaoming and Xiaogang go to the grain and oil store twice a month to help their mother buy oil. The oil price has been changed twice. The first oil price is X yuan per kilogram, and the second oil price is Y yuan per kilogram, but each of them buys oil in a different way. Xiaoming buys the same quality oil every time, while Xiaogang only spends the same amount of money to buy oil every time. Which of the two methods is cost-effective?

Solution process and format standard of fractional order equation