And 71= 7,72 = 49,73 = 343,74 = 2401,7 5 = 16807.
It can be seen that the unit numbers are: 7, 9, 3, 1, 7 ... Every fourth power cycle, 777= 194*4+ 1.
So 7 777 is the same as 7 1 digit, and 7 1 = 7, so the result is 7.
2. The principle is the same as above, and the 9 n law is 9, 1, 9, 1...2 cycles. 123456789 divided by 2 equals 1.
So, like 9 1 = 9, the answer is 9.
To find a number, just add all the numbers in the formula. The corresponding single digits of each item are as follows:
1! —— 1,2! ——2,3! ——6,4! ——4,5! ——0
Starting from 6, because the unit is 0 * n = 0(n >；; 5)
Add it all up: 1+2+6+4+0+0 = 12, so the result is 2.
4. The power of 100 1 3 is the method of problem 1, and the unit number is 3, 9, 7, 1, 3 ...1001-20.
The power of 17 of 1002 is 7, 9, 3, 1, 7... 1002- 1000 = 2, and the result is 9;
The power of 19 of 1003 is 9, 1, 9, 1, ...1003-1002 =1,and the result is 9;
1×9×9=8 1, so the total result is 1.
The answers to questions 1 to 4 are as follows:
1、7
2、9
3、2
4、 1