✔ 最佳答案
(1)
20 = 2^2 ×5
30 = 2 ×3 ×5
正公因數有 2、 5、 10
(2)
最大公因數 (20,30) =10
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(150 , 180 , 240 ) = 5×6 =30
150 = 5^2 ×6
180 = 5 ×6^2
240 = 2^3 × 5 ×6
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([ -64 , 72] , 240) = (576 , 240) =48
先取得 -64,72之最小公倍數(取正數),
然後此數再與240取最大公因數(取正數)
[ -64 , 72] = 2^6 × 3^2 =576
64 = 2^6
72 = 2^3 × 3^2
(576 , 240) = 2^4 × 3 =48
576 = 2^6 × 3^2
240 = 2^4 × 3 × 5