a)2025^2019-2024×2025^2018. =
2025^2018 × (2025^1 - 2024 × 1) =
2025^2018 × (2025 - 2024) =
2025^2018 × 1 =
2025^2018
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b) (7^10 - 7^9) : (7^9 - 7^8) =
7^9 × (7^1 - 1) : 7^8 × (7^1 - 1) =
(7^9 × 6) : (7^8 × 6) =
7^9 : 7^8 × 6 : 6 =
7^1 × 1 =
7
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