Answer:
steps below
Step-by-step explanation:
5¹+5² = 30 30/6 = 5¹
5³+5⁴ = 125 + 625 = 750 750/6 = 125 = 5³
5⁵+5⁶ = 18750 18750/6 = 3125 = 5⁵
...........
(5¹⁹⁹¹+5¹⁹⁹²)/6 = 5¹⁹⁹¹
sum of every couple consecutive multiple of 5 are multiple of 6, the sum
S= 5+ 5^2 + 5^3 + ...+ 5^1991 + 5 ^1992 IS multiple of 6
