[問題] 問一題數學
6信不同,4郵筒不同,每郵筒至少投入一封信,有(1560)種
詳解
4^6-(4x3^6-6x2^6+4x1)=1560
請問 ^^^^為什麼是減號?
全部減掉(一個郵筒沒信+兩個郵筒沒信+三個郵筒沒信)
這樣對嗎?
麻煩大家幫我解答
謝謝
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