hey I should perhaps have seminar presentation on this task and wonder if that evidence is good enough?

show that the 5^(n +1) -1 is divisible by 4, for all n> _ = 0 (greater or equal to 0)

my solve:

5^(n+1)-1

5≡1 (mod 4)

5^(n+1) = 5^n*5≡ 1^n*1 (mod 4)

1^n*1-1≡0 (mod 4)

1^n = 1 n> _ = 0 (greater or equal to 0)

1-1≡0 (mod 4)

what i would prove