Ch\u00fang ta h\u00e3y l\u00e0m m\u1ed9t cu\u1ed9c du l\u1ecbch th\u00fa v\u1ecb v\u00e0o th\u1ebf gi\u1edbi nh\u1eefng con s\u1ed1. M\u1eddi c\u00e1c b\u1ea1n tu\u1ef3 \u00fd vi\u1ebft m\u1ed9t con s\u1ed1 c\u00f3 ba ch\u1eef s\u1ed1 (ph\u1ea3i c\u00f3 c\u00e1c ch\u1eef s\u1ed1 kh\u00f4ng ho\u00e0n to\u00e0n gi\u1ed1ng nhau) sau \u0111\u00f3 s\u1eafp x\u1ebfp c\u00e1c ch\u1eef s\u1ed1 trong con s\u1ed1 t\u1eeb l\u1edbn \u0111\u1ebfn b\u00e9 ta s\u1ebd thu \u0111\u01b0\u1ee3c m\u1ed9t s\u1ed1 m\u1edbi. Sau \u0111\u00f3 l\u1ea1i s\u1eafp x\u1ebfp c\u00e1c ch\u1eef s\u1ed1 trong s\u1ed1 v\u1eeba thu \u0111\u01b0\u1ee3c theo th\u1ee9 t\u1ef1 ng\u01b0\u1ee3c l\u1ea1i t\u1eeb b\u00e9 \u0111\u1ebfn l\u1edbn ta l\u1ea1i \u0111\u01b0\u1ee3c m\u1ed9t s\u1ed1 kh\u00e1c. T\u00ecm hi\u1ec7u s\u1ed1 c\u1ee7a hai s\u1ed1 v\u1eeba m\u1edbi nh\u1eadn \u0111\u01b0\u1ee3c. L\u1eb7p l\u1ea1i c\u00e1c b\u01b0\u1edbc nh\u01b0 v\u1eeba ti\u1ebfn h\u00e0nh v\u1edbi hi\u1ec7u s\u1ed1 v\u1eeba m\u1edbi nh\u1eadn \u0111\u01b0\u1ee3c. X\u00e9t xem b\u1ea1n s\u1ebd nh\u1eadn \u0111\u01b0\u1ee3c k\u1ebft qu\u1ea3 nh\u01b0 th\u1ebf n\u00e0o:<\/p>\n\n\n\n
V\u00ed d\u1ee5 ch\u1ecdn s\u1ed1 323. Sau b\u01b0\u1edbc s\u1eafp x\u1ebfp th\u1ee9 nh\u1ea5t ra c\u00f3 c\u00e1c s\u1ed1 332, sau b\u01b0\u1edbc th\u1ee9 hai s\u1ebd l\u00e0 s\u1ed1 233. Hi\u1ec7u s\u1ed1 c\u1ee7a hai s\u1ed1 n\u00e0y s\u1ebd l\u00e0 099. (S\u1ed1 099 c\u0169ng l\u00e0 s\u1ed1 c\u00f3 3 ch\u1eef s\u1ed1). L\u1ea1i ti\u1ebfp t\u1ee5c thao t\u00e1c c\u00e1c b\u01b0\u1edbc ti\u1ebfp theo v\u00e0 ti\u1ebfp t\u1ee5c thu nh\u1eadn \u0111\u01b0\u1ee3c c\u00e1c s\u1ed1 990 – 099 = 891; 981 – 189 = 792; 792 – 279 = 693; 693 – 396 = 594; 954 – 459 = 495; 954 – 495 = 495\u2026 Sau m\u1ed9t s\u1ed1 b\u01b0\u1edbc bi\u1ebfn \u0111\u1ed5i con s\u1ed1 \u0111\u01b0a ra ban \u0111\u1ea7u \u0111\u00e3 chui v\u00e0o \u201ct\u00fai\u201d v\u00e0 d\u1eebng l\u1ea1i \u1edf s\u1ed1 495.<\/p>\n\n\n\n
Th\u1ebf v\u1edbi c\u00e1c s\u1ed1 4 ch\u1eef s\u1ed1 th\u00ec s\u1ebd ra sao? K\u1ebft qu\u1ea3 \u0111\u01b0\u1ee3c kh\u1eb3ng \u0111\u1ecbnh l\u00e0 v\u1edbi c\u00e1c s\u1ed1 c\u00f3 4 ch\u1eef s\u1ed1 th\u00ec c\u00e1c b\u01b0\u1edbc bi\u1ebfn \u0111\u1ed5i s\u1ebd d\u1eebng l\u1ea1i \u1edf s\u1ed1 6174.<\/p>\n\n\n\n
\u0110i\u1ec1u n\u00e0y d\u01b0\u1eddng nh\u01b0 c\u00e1c lo\u1ea1i s\u1ed1 \u0111\u00e3 n\u00eau tr\u00ean \u0111\u00e3 chui v\u00e0o c\u00e1c \u201ch\u1ed1 \u0111en\u201d trong to\u00e1n h\u1ecdc v\u00e0 kh\u00f4ng ra kh\u1ecfi \u0111\u01b0\u1ee3c n\u1eefa.<\/p>\n\n\n\n
Nh\u00e0 to\u00e1n h\u1ecdc Li\u00ean X\u00f4 c\u0169 Kasimov trong s\u00e1ch \u201cC\u1ea3m nh\u1eadn to\u00e1n h\u1ecdc\u201d \u0111\u00e3 t\u1eebng vi\u1ebft \u201c\u0110\u00e2y l\u00e0 b\u00ed m\u1eadt kh\u00f4ng c\u00f3 l\u1eddi gi\u1ea3i\u201d.<\/p>\n\n\n\n
Ng\u01b0\u1eddi ta cho r\u1eb1ng \u201ch\u1ed1 \u0111en\u201d kh\u00f4ng ch\u1ec9 c\u00f3 m\u1ed9t s\u1ed1 m\u00e0 c\u00f3 th\u1ec3 c\u00f3 nhi\u1ec1u s\u1ed1 xu\u1ea5t hi\u1ec7n nh\u01b0 c\u00e1c h\u00ecnh trong \u0111\u00e8n k\u00e9o qu\u00e2n ho\u1eb7c gi\u1ed1ng nh\u01b0 h\u00ecnh t\u01b0\u1ee3ng T\u00f4n Ng\u1ed9 Kh\u00f4ng l\u1ea1c v\u00e0o b\u00e0n tay c\u1ee7a Ph\u1eadt t\u1ed5 Nh\u01b0 Lai.<\/p>\n\n\n\n
V\u00ed nh\u01b0 c\u00e1c s\u1ed1 c\u00f3 n\u0103m ch\u1eef s\u1ed1 ng\u01b0\u1eddi ta ph\u00e1t hi\u1ec7n hai \u201cd\u00e3y\u201d \u0111\u00f3 l\u00e0: {63954, 61794, 62962, 75933} v\u00e0 {62964, 71973, 83952, 74943}. N\u1ebfu c\u00e1c b\u1ea1n th\u1ea5y c\u00f3 h\u1ee9ng th\u00fa th\u00ec h\u00e3y th\u1eed xem.<\/p>\n\n\n\n
T\u1eeb kho\u00e1: S\u1ed1 nh\u1ea3y v\u00e0 h\u1ed1 \u0111en.<\/p>\n\n\n\n
<\/p>\n\n\n\n\n\n\n","protected":false},"excerpt":{"rendered":"
Ch\u00fang ta h\u00e3y l\u00e0m m\u1ed9t cu\u1ed9c du l\u1ecbch th\u00fa v\u1ecb v\u00e0o th\u1ebf gi\u1edbi nh\u1eefng con s\u1ed1. M\u1eddi c\u00e1c b\u1ea1n tu\u1ef3 \u00fd vi\u1ebft m\u1ed9t con s\u1ed1 c\u00f3 ba ch\u1eef s\u1ed1 (ph\u1ea3i c\u00f3 c\u00e1c ch\u1eef s\u1ed1 kh\u00f4ng ho\u00e0n to\u00e0n gi\u1ed1ng nhau) sau \u0111\u00f3 s\u1eafp x\u1ebfp c\u00e1c ch\u1eef s\u1ed1 trong con s\u1ed1 t\u1eeb l\u1edbn \u0111\u1ebfn b\u00e9 ta s\u1ebd […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_disable_autopaging":false},"categories":[15,9],"tags":[],"class_list":["post-7501","post","type-post","status-publish","format-standard","hentry","category-hoi-dap-khoa-hoc","category-toan-hoc"],"_links":{"self":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/7501","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/comments?post=7501"}],"version-history":[{"count":0,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/7501\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/media?parent=7501"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/categories?post=7501"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/tags?post=7501"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}