0 3 8 15 … 1 2 7 14 … 4 5 6 13 … 9 10 11 12 … … … … … … A series of natural numbers 0,1,2,3 ,2005,…… , 2024, the first number is 0, starting from the second number, each one is larger than the previous one, and the last one is 2024 What is the row and column of 2005?

0 3 8 15 … 1 2 7 14 … 4 5 6 13 … 9 10 11 12 … … … … … … A series of natural numbers 0,1,2,3 ,2005,…… , 2024, the first number is 0, starting from the second number, each one is larger than the previous one, and the last one is 2024 What is the row and column of 2005?

Rule: take 0 as the fixed point, from the upper left corner to the lower right corner, form a square with numbers in turn, because 0 does not form a square, then the bottom edge of the nth square from left to right is n ^ 2, n ^ 2 + 1 N ^ 2 + N, and then along the right from bottom to top are n ^ 2 + N, n ^ 2 + N + 1, n ^ 2 + N + 2 So, 2005 = 44 ^ 2 + 6

Among the 30 people, 21 got the first question right, 18 got the second question right, 4 got both questions wrong, and several got both questions right
Among the 30 people, 21 got the first question right, 18 got the second question right, 4 got both questions wrong, and how many got both questions right?

Duyu = 21 + 18-30 + 4 = 13

The teacher gave two math problems. Among the 30 students, 21 got the first problem right and 18 got the second problem right. How many people got both problems right at least?

21 + 18 = 30 = 39 - 30 = 9 (person) answer: at least 9 people do both questions right

The teacher gave two math problems. Among the 30 students, 21 got the first problem right and 18 got the second problem right. How many people got both problems right at least?

21 + 18 = 30 = 39 - 30 = 9 (person) answer: at least 9 people do both questions right