3 4 = 8 1, 1998/4 = 499 Yu 2
3^ 1998=
(3^4)^499
*
3^2
Of which (3 4) 499
The unit number is 1,
3 2 digits are: 9, 1*9=9,
So the digit of 3 1998 is 9.
Second,
5 to the power of 1999:
What is the power of five digits?
The power of 1999 of 5 is 5.
Three,
7 4 = 8 1, the unit number is1.
2000/4=500,
7^2000=(7^4)^500
So the unit number of 7 to the 2000th power is 1.
The unit number is 9*5* 1=45, and the unit number is 5.
The unit number is 5.