Choose a, the original series: -2, 0, 2, 4, 6 (arithmetic progression).

Every number+1 is squared again: 1, 1, 9, 25, 49.

2. 12 12 18() 162 = = = = = = = A24 B30 C36 D42

Choose C, and multiply the first two numbers by the arithmetic progression with the third number of 8, 6 and 4.

3。 There are 25 large and small stations on a railway line. So how many different tickets should be prepared for this railway?

There are 24 different kinds of tickets from the first station to the other 24 stations.

There are 24 different kinds of tickets from the second station to the other 24 stations.

…………

One ***25 workstations: 25X24=600

(Note: The ticket from Station A to Miley Miley is different from the ticket from Miley Miley to Station A)

You can also calculate all the way first and then multiply it by 2: (1+2+3+4+...+24) x2 = 600.