Answers

2015-07-19T20:00:23+08:00

This Is a Certified Answer

×
Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
We only need to look at the last digit.
7 ^ 1998 ^ 1999

The pattern of the units digit of 7 
When exponent is divided by 4,
r1     r2     r3     r0
7      9       3      1

Take note that when we divide by 4 we only need to look at the last two digits.

When 1998 is divided by 4 we have a remainder of 2, 1999 we would have a remainder of 3.
Then the remainder of 1998*1999 when divided by 4 is (2*3)mod 4 = 6 mod 4 = 2 mod 4

Therefore the last digit would be 9.
0