How to calculate 2 + 22 + 222 +. 2222?
This can be multiplied by the number of digits. For example, you can multiply by the number of digits by the number of digits: 2 * 1 + 2 * 2 + 2 * 3 + 2 * 4 + 2 * 5 + 2 * 6 + 2 * 7 and so on 2222222 ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^?
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- 1. [high school sequence] do you know that three consecutive terms can be used to find the general formula of the sequence In the stem of the question, I only said that this is a sequence of positive numbers, and I also gave a formula. The first question is to find a1a2a3, and the second question is to find the general term formula. I derived A1, A2, A3. Can I use a3-a2 = a2-a1 = D or A3 / A2 = A2 / A1 = q to find the general term formula? Or should I use the formula given by the stem of the question to prove it? Although I have made the correct answer in both methods. The question is a little long. No point. Who will answer, It is known that {an} is a sequence of positive numbers, and the median of the equal difference between an and 2 is equal to the median of the equal ratio between Sn and 2. I calculate A1 = 2, A2 = 6, A3 = 10, Then the second question can be directly explained as arithmetic sequence according to a3-a2 = a2-a1 = D? How to answer the questions in the exam? I feel too confused and want to close this question
- 2. 2+22+222+2222+…… +What is 2222?
- 3. 2 + 22 + 222 + 2222 + 22222 + -- + 2222, please use a simple method to calculate
- 4. 50-49+48-47+46-… +4-3 + 2-1, simple algorithm
- 5. Fill in the blanks in the first day of junior high school! 1×2=1/3×1×2×3,1×2+2×3=1/3×2×3×4,1×2+2×3+3×4+4×5 =1/3×4×5×6,... According to the above rule, please guess: 1 × 2 + 2 × 3 + 3 × 4 +... + n (n + 1) (n is an integer)=------------- Very urgent ah, help, the right answer plus 50 points ah, speed!
- 6. There is a column of numbers as follows: 4, 5, 9, 14, 23. What is the number 1999?
- 7. There is a column of numbers, 2, 5, 8, 11, 14 Then 104 is the () th number in this column A. 33B. 32C. 34D. 35
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- 11. What are the rules of the results of 2 * 22 * 22 222 * 222 2222 * 2222 22222 * 22222
- 12. The law of sequence 1,4,13,40121 ·
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- 19. Known Fibonacci sequence: 1,2,3,5,8,13,21,34,55. There are several even numbers in the first 2003 items of this sequence
- 20. 1、0、1、0、1、0、1、…… What is the general term formula of?