☰ Contents1.2 · The Fundamental Theorem of Arithmetic25/101
Putting it to work: can 4ⁿ end in 0?
A number ends in 0 only if 10 = 2 × 5 divides it — so it needs a factor of 5. But 4n = (22)n = 22n: nothing but 2s. Uniqueness guarantees no 5 can sneak in — so 4n never ends in 0.