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tomvuivui
2 năm trước
a) tìm số tự nhiên có hai chữ số khác nhau. Biết rằng, hai chữ số của số đó đều là số nguyên tố . Tích của số đó với các chữ số của nó là số có 3 chữ số giống nhau được tạo thành từ chữ số hàng đơn vị của số đó b) cho P là số nguyên tố (P>3) và 2p+1 cũng là số nguyên tố. Hỏi 4 p + 1 là số nguyên tố hay hợp số ?vì sao?
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