Bình phương của một số nguyên lẻ
#1
Đã gửi 06-07-2011 - 06:59
Discovery is a child’s privilege. I mean the small child, the child who is not afraid to be wrong, to look silly, to not be serious, and to act differently from everyone else. He is also not afraid that the things he is interested in are in bad taste or turn out to be different from his expectations, from what they should be, or rather he is not afraid of what they actually are. He ignores the silent and flawless consensus that is part of the air we breathe – the consensus of all the people who are, or are reputed to be, reasonable.
Grothendieck, Récoltes et Semailles (“Crops and Seeds”).
#2
Đã gửi 21-07-2011 - 18:23
Giả sử $p=a^3-b^3=(a-b)(a^2+ab+b^2)$. Vì $a,b$ là các số nguyên Dương nên ta có $a^2+ab+b^2>1$, mà $p$ nguyên tố suy ra $a-b=1$, nên $a=1+b$. Thay vào ta có $p=3b^2+3b+1$, suy ra $4p=12b^2+12b+4=3(2b+1)^2+1$.
Như vậy có nghĩa là $4p$ chia $3$ được thương là $(2b+1)^2$ và dư $1$. Ta có đpcm.
Bài viết đã được chỉnh sửa nội dung bởi Phạm Quang Toàn: 02-08-2011 - 17:13
Discovery is a child’s privilege. I mean the small child, the child who is not afraid to be wrong, to look silly, to not be serious, and to act differently from everyone else. He is also not afraid that the things he is interested in are in bad taste or turn out to be different from his expectations, from what they should be, or rather he is not afraid of what they actually are. He ignores the silent and flawless consensus that is part of the air we breathe – the consensus of all the people who are, or are reputed to be, reasonable.
Grothendieck, Récoltes et Semailles (“Crops and Seeds”).
#3
Đã gửi 02-08-2011 - 17:07
$p=a^3-b^3=(a+b)(a^2+ab+b^2)$.
hình như bạn nhầm chỗ này, đáng ra phải là: $p=a^3-b^3=(a-b)(a^2+ab+b^2)$ chứ nhỉ
Bạn xem lại hồ mình cái
Ác Ma Học Đường- Cá Sấu
#4
Đã gửi 02-08-2011 - 17:13
Discovery is a child’s privilege. I mean the small child, the child who is not afraid to be wrong, to look silly, to not be serious, and to act differently from everyone else. He is also not afraid that the things he is interested in are in bad taste or turn out to be different from his expectations, from what they should be, or rather he is not afraid of what they actually are. He ignores the silent and flawless consensus that is part of the air we breathe – the consensus of all the people who are, or are reputed to be, reasonable.
Grothendieck, Récoltes et Semailles (“Crops and Seeds”).
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