prove that the tens digit of every power integral power of 3 is an even number.
like 3^5 = 243. here it is 4.
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1 Answers
Shubhodip
·2011-11-04 00:49:40
3^l\equiv 3,9,7,1 \pmod {10} when l\equiv 1,2,3,0 \pmod{4} respectively. Easy to check that 3^l\equiv 3,9,7,1\pmod{20} when l\equiv 1,2,3,0 \pmod{4} respectively. So the claim is true...