9514 1404 393
Answer:
factor out 5^19
Step-by-step explanation:
a) Reason from parity:
both 5^20 and 5^19 are products with only odd numbers (5) as factors. Hence each is an odd number. The difference of odd numbers is always even.
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b) Factor:
5^20 -5^19 = 5^19(5 -1) = 5^19×4
This product has an even factor (4), so is even.
