N\u1ebfu ch\u1ec9 d\u00f9ng \u0111\u1ed3ng 1 xu. Ch\u1ec9 c\u00f3 m\u1ed9t c\u00e1ch.<\/p>\n\n\n\n
D\u00f9ng \u0111\u1ed3ng 2 xu k\u1ebft h\u1ee3p \u0111\u1ed3ng 1 xu. Vi\u1ec7c s\u1eed d\u1ee5ng \u0111\u1ed3ng 2 xu c\u00f3 th\u1ec3 d\u00f9ng t\u1eebng \u0111\u1ed3ng k\u1ebft h\u1ee3p v\u1edbi \u0111\u1ed3ng 1 xu, d\u00f9ng hai \u0111\u1ed3ng 2 xu k\u1ebft h\u1ee3p, d\u00f9ng ba \u0111\u1ed3ng 2 xu k\u1ebft h\u1ee3p, d\u00f9ng b\u1ed1n \u0111\u1ed3ng 2 xu k\u1ebft h\u1ee3p \u0111\u1ed3ng 1 xu v\u00e0 d\u00f9ng n\u0103m \u0111\u1ed3ng 2 xu. Nh\u01b0 v\u1eady t\u1ea5t c\u1ea3 c\u00f3 n\u0103m c\u00e1ch.<\/p>\n\n\n\n
D\u00f9ng m\u1ed9t \u0111\u1ed3ng 5 xu k\u1ebft h\u1ee3p v\u1edbi d\u00f9ng n\u0103m \u0111\u1ed3ng 1 xu; d\u00f9ng m\u1ed9t \u0111\u1ed3ng 2 xu v\u00e0 ba \u0111\u1ed3ng 1 xu; d\u00f9ng hai \u0111\u1ed3ng 2 xu v\u00e0 1 \u0111\u1ed3ng m\u1ed9t xu. Nh\u01b0 v\u1eady c\u00f3 t\u1ea5t c\u1ea3 ba c\u00e1ch.<\/p>\n\n\n\n
D\u00f9ng hai \u0111\u1ed3ng 5 xu, ch\u1ec9 c\u00f3 m\u1ed9t c\u00e1ch.<\/p>\n\n\n\n
Theo nh\u01b0 m\u00f4 t\u1ea3 t\u1ed5ng s\u1ed1 c\u00e1ch s\u1eafp x\u1ebfp s\u1ebd l\u00e0 1 + 5 + 3 + 1 = 10 c\u00e1ch.<\/p>\n\n\n\n
Th\u1ebf nh\u01b0ng ngo\u00e0i c\u00e1ch ph\u00e2n t\u00edch tr\u1ef1c ti\u1ebfp nh\u01b0 tr\u00ean li\u1ec7u c\u00f2n c\u00f3 ph\u01b0\u01a1ng ph\u00e1p t\u1ed5ng qu\u00e1t h\u01a1n kh\u00f4ng? C\u00f3. B\u1ea1n ch\u1ec9 c\u1ea7n t\u00ednh h\u1ec7 s\u1ed1 A10 c\u1ee7a s\u1ed1 h\u1ea1ng x10 c\u1ee7a c\u00f4ng th\u1ee9c d\u01b0\u1edbi \u0111\u00e2y: (1 + x + x2 + x3 + x4 + x5 + x6 + x7 + x8 + x9 + x10). (1 + x + x2 +x4 + x6 + x8 +x10). 1 + x5 + x10 = 1 + A1x + A2x + \u2026A10x10 + \u2026+ x30<\/p>\n\n\n\n
Th\u1ebf A10 b\u1eb1ng bao nhi\u00eau v\u1eady?<\/p>\n\n\n\n
Hai s\u1ed1 h\u1ea1ng x10 \u1edf hai nh\u00e2n t\u1eed tr\u01b0\u1edbc nh\u00e2n v\u1edbi s\u1ed1 1, \u1edf nh\u00e2n t\u1eed th\u1ee9 3 l\u00e0 s\u1ed1 h\u1ea1ng ch\u1ee9a x10, c\u00e1c lu\u1ef9 th\u1eeba x2 nh\u00e2n v\u1edbi x8 v\u00e0 x4 nh\u00e2n v\u1edbi x6 \u0111\u1ec1u \u0111\u01b0\u1ee3c x10 t\u1ea5t c\u1ea3 c\u00f3 s\u00e1u s\u1ed1 h\u1ea1ng ch\u1ee9a x10.<\/p>\n\n\n\n
Hai s\u1ed1 h\u1ea1ng ch\u1ee9a x5 \u1edf nh\u00e2n t\u1eed \u0111\u1ea7u, v\u1edbi \u1edf nh\u00e2n t\u1eed th\u1ee9 3 ta c\u0169ng thu \u0111\u01b0\u1ee3c x10. B\u1edfi v\u00ec \u1edf nh\u00e2n t\u1eed th\u1ee9 hai, t\u1ea5t c\u1ea3 c\u00e1c lu\u1ef9 th\u1eeba c\u1ee7a x \u0111\u1ec1u l\u00e0 s\u1ed1 ch\u1eb5n n\u00ean ch\u1ec9 c\u00f3 x5 v\u00e0 x3 v\u00e0 x2, x1 v\u00e0 x4 l\u00e0 3 c\u00e1ch t\u1ea1o \u0111\u01b0\u1ee3c x5, n\u00ean ta ch\u1ec9 c\u00f3 3×10.<\/p>\n\n\n\n
Cu\u1ed1i c\u00f9ng s\u1ed1 1 \u1edf hai nh\u00e2n t\u1eed c\u00f2n l\u1ea1i nh\u00e2n v\u1edbi x10 l\u00e0 \u0111\u01b0\u1ee3c m\u1ed9t s\u1ed1 h\u1ea1ng ch\u1ee9a x10. T\u1ed5ng c\u00e1c s\u1ed1 h\u1ea1ng c\u00f3 ch\u1ee9a x10 nh\u01b0 v\u1eeba m\u00f4 t\u1ea3 \u1edf tr\u00ean ta c\u00f3<\/p>\n\n\n\n
A10 = 6 + 3 + 1 = 10.<\/p>\n\n\n\n
Ta l\u1eb7p l\u1ea1i k\u1ebft qu\u1ea3 \u0111\u00e3 nh\u1eadn \u0111\u01b0\u1ee3c \u1edf ph\u01b0\u01a1ng ph\u00e1p ph\u00e2n t\u00edch tr\u1ef1c ti\u1ebfp tr\u00ean kia.<\/p>\n\n\n\n
Ph\u01b0\u01a1ng ph\u00e1p v\u1eeba tr\u00ecnh b\u00e0y \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 \u201cph\u00e9p to\u00e1n h\u00e0m s\u1ed1 g\u1ed1c\u201d. Ph\u01b0\u01a1ng ph\u00e1p quan tr\u1ecdng n\u00e0y \u0111\u01b0\u1ee3c nh\u00e0 to\u00e1n h\u1ecdc Thu\u1ef5 S\u0129 \u01a0le \u0111\u01b0a ra.<\/p>\n\n\n\n
N\u1ebfu nh\u01b0 c\u1ea7n t\u00ecm c\u00e1ch s\u1eafp x\u1ebfp c\u00e1c \u0111\u1ed3ng 1 xu, 2 xu, 5 xu, 1 h\u00e0o, 2 h\u00e0o, 5 h\u00e0o \u0111\u1ec3 \u0111\u01b0\u1ee3c \u0111\u1ee7 1 \u0111\u1ed3ng (100 xu) h\u1ecfi ph\u1ea3i c\u00f3 bao nhi\u00eau c\u00e1ch s\u1eafp x\u1ebfp, v\u1edbi tr\u01b0\u1eddng h\u1ee3p n\u00e0y vi\u1ec7c t\u00ednh d\u1ef1a v\u00e0o ph\u00e2n t\u00edch tr\u1ef1c ti\u1ebfp \u0111\u00e3 tr\u1edf n\u00ean r\u1ea5t kh\u00f3 kh\u0103n. Nh\u01b0ng n\u1ebfu d\u00f9ng \u201cph\u01b0\u01a1ng ph\u00e1p h\u00e0m s\u1ed1 g\u1ed1c\u201d ta s\u1ebd c\u00f3 c\u00f4ng th\u1ee9c. (1 + x + x2 + x3 +\u2026+x100). (1 + x2 + x4 +\u2026+ x100) (1 + x5 + x10 +\u2026 + x100). (1 + x10 + x20 +\u2026 + x100) (1 + x20 + x40 +\u2026 + x100) .(1 + x50 + x100)<\/p>\n\n\n\n
Ta ch\u1ec9 c\u1ea7n khai tri\u1ec3n ch\u00fang v\u00e0 t\u00ecm h\u1ec7 s\u1ed1 A100 c\u1ee7a s\u1ed1 h\u1ea1ng ch\u1ee9a x100. Nh\u1edd thao t\u00e1c m\u00e1y m\u00f3c n\u00e0y, nh\u1edd c\u00e1c m\u00e1y t\u00ednh \u0111i\u1ec7n t\u1eed ta c\u00f3 th\u1ec3 d\u1ec5 d\u00e0ng th\u1ef1c hi\u1ec7n v\u00e0 t\u00ecm \u0111\u01b0\u1ee3c gi\u1ea3i ph\u00e1p.<\/p>\n\n\n\n
T\u1eeb kho\u00e1: H\u00e0m s\u1ed1 g\u1ed1c.<\/p>\n\n\n\n
<\/p>\n\n\n\n\n\n\n","protected":false},"excerpt":{"rendered":"
N\u1ebfu ch\u1ec9 d\u00f9ng \u0111\u1ed3ng 1 xu. Ch\u1ec9 c\u00f3 m\u1ed9t c\u00e1ch. D\u00f9ng \u0111\u1ed3ng 2 xu k\u1ebft h\u1ee3p \u0111\u1ed3ng 1 xu. Vi\u1ec7c s\u1eed d\u1ee5ng \u0111\u1ed3ng 2 xu c\u00f3 th\u1ec3 d\u00f9ng t\u1eebng \u0111\u1ed3ng k\u1ebft h\u1ee3p v\u1edbi \u0111\u1ed3ng 1 xu, d\u00f9ng hai \u0111\u1ed3ng 2 xu k\u1ebft h\u1ee3p, d\u00f9ng ba \u0111\u1ed3ng 2 xu k\u1ebft h\u1ee3p, d\u00f9ng b\u1ed1n \u0111\u1ed3ng 2 xu […]<\/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-7571","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\/7571","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=7571"}],"version-history":[{"count":0,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/7571\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/media?parent=7571"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/categories?post=7571"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/tags?post=7571"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}