a^b where a,b is N
in this type of question always find period of variation of unit place
eg.. in ur question 9^b i.e... 9,1,9,1... period is 2 therefore for even power it is 1
and for odd power it is 9
u can try it for other problem also
E.G..... find unit place of 143^86
in this 3^b then period is 4
and rem(86 / 4) = 2
that's imples unit place digit is 9
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