we assume that p(n) is true for n=k
5k?- 5 = 4m
5k?= 4m+5 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?(i)
now we will show for n=k+1
5?k+1?- 5
5?k.51?- 5
using (i)
(4 m+5).5 - 5
20 m + 25 - 5
20 m +20
4 ( 5 m + 5)
Hence p(n) is true for n =(k + 1)
Hence proved.
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