Question

81的7次方减27的9次方再减9的13次方能被5整除吗?

Answer 1

81^7-27^9-9^13

=(3^4)^7-(3^3)^9-(3^2)^13

=3^28-3^27-3^26

=3^26(9-3-1)

=3^26*5

=3^2*5*3^24

=45*3^24

=5^2*3^25

所以能被5整除