✨ 最佳解答 ✨
9.
【★ a^b = a 的 b 次方】
3^12 - 3^10
= 3^2 × 3^10 - 3^10
= 3^10(9 - 1)
= 8 × 3^10
所以前面剩下 3^10
3^11 + 3^9
= 3^2 × 3^9 + 3^9
= 3^9(9 + 1)
= 10 × 3^9
所以後面剩下 2 × 3^9
原式 = 3^10 - 2 × 3^9
= 3 × 3^9 - 2 × 3^9
= 3^9(3 - 2)
= 3^9 --> a = 9 #
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10.
次方相乘有幾位數,找不到國中作法。
3^2 × 5^48 × 7 × 8^17
=> 3^2 × 5^48 × 7 × (2^3)^17
= 2^51 × 3^2 × 5^48 × 7
51 × log2 + 2 × log3 + 48 × log5 + log7
= 51 × 0.3010 + 2 × 0.4771 + 48 × 0.6990 + 0.8451
= 50.3423 => 有 51 位數 #
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17.
一開始【紅豆】比【綠豆】多 56 - 24 = 32 顆
分成兩堆,其中一堆 【紅豆】比【綠豆】多 12 顆
--> 另外一堆 【紅豆】比【綠豆】多 32 - 12 = 20 顆 #
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