NGHIEN CUU & UNG DUNG mpT 5D DnnE HORT apnG ED HDC, ani SD THUdnE E^P tl TRUdnE TRUDE HDC CD Sd I Hoaf dgng So hgc vd chung Idn nhat, bgi chung nhd Dai so nhat, tinh lo^n gid tri ciia hdm Trong day hg[.]
NGHIEN CUU & UNG DUNG mpT 5D DnnE HORT apnG ED HDC, ani SD THUdnE E^P tl TRUdnE TRUDE HDC CD Sd TS T r a n A n h Tuan Trudng CDSP Nghf An I Hoaf dgng So hgc vd Dai so Trong day hgc Sd hgc (SH) va Dai so (DS) d trudng Trung hgc CO sd (THCS), gido vicn (GV) td chirc cho hgc sinh (HS) hoat dgng tren cdc ngi dung Toan hgc nhu: Nhfl-ng kien thiic md ddu vc sd (tir sd ty nhien den sd thyc); Cdc bieu thiic DS; Phuang trinh bdc nhat, b^c hai; He phuong trinh; Bdt phuang trinh bdc nhdt; Ham sd; Mgt vdi dang ham sd don gian va dd thi ciia chiing, chung tdi quan niem dd Id td chiic cac hoat ddng SH, DS Moi hoat ddng SH, DS Id mdt tinh hudng cd vdn de ggi dgng ca hgc tap SH vd DS Mgt so dang hoat dgng SH, DS thudng gap d tru-dng THCS Hoat ddng SH, DS thudng gap day hgc SH va DS d trudng THCS bao gdm: 2.1- Hogt dgng tinh todn, thuc hdnh a Muc dich: Hinh kT ndng tinh toan, thuc hien cdc phep tinh hgc toan vd boat dgng thyc tien cua HS b Ngi dung: Ngi dung hoat dgng tinh todn, thyc hdnh bao gdm: thuc hien cac phep tinh tren cdc sd vd cdc dang thyc hanh khde nhu: nit ggn phan sd, qui ddng mdu so, tim udc chung Idn nhat, bgi chung nhd nhat, tinh lo^n gid tri ciia hdm sd tgi mgt gid tri cua doi so ^,, ,^'''I.V 43 4.M343 Chung to rSng:— = S8S888 i)i} giai bai todn nay, HS ed thl thir: 43 x 888888 - 88 x 434343 Tuy nhicn, cd the sir dyng tinh chdt ciia SH phan tich Chdng han, phdn tich da thap phan tir sd va mau sd dc thuc: f(x) = X 6x + nhdn tii Cd the diing cac each giai bdi todn khde nhu: tdeh sd haog, Ta cd: 434343 - 430000 + 4300 + 43 them bdt cimg mdt hang tu, = ( 0 0 + 0 + ) hodc thyc hien phep chia f(x) cho (x-1) ta cd ket qua f(x) = = x lOlOl 888888 = 880000 + 8800 + 88 (x-I)(x-5) 3- Hogt dgng gidi phucmg -88(10000+100+1) trinh, bdt phirang trinh, hf = 8 x 1010! Theo tinh chdt co bdn ciia phuang trinh - Hogt dgng gidi phuong phan sd thi: trinh (bdt phucmg trinh) c6 434343_43xl0101_43 88x10101 88 nghTa Id tim mgi gid tri ciia cac 2.2' Hogt dgng bien doi an ldm cho phucmg trinh (bat phuang trinh) trd dang bieu thuc « Mijc dich: Giiip HS van thlie (bdt ddng thiic) dung (cac gid tri dd ciia dn ggi la nghiem dyng cac kien thirc da hgc tien hanh bien ddi bai todn ve dang ciia phuong trinh (bdt phucmg trinh)), hoac chung minh rang phil hgp de gidi bdi toan dd b Ngi dimg: Ngi dung hoat khdng cd nhihig gid tri nao dgng bien ddi bieu thuc bao nhu vgy gdm: bien ddi, nit ggn cdc - Tap hgp cdc phuang trinh bieu thuc sd; bien ddi cdc bieu ddi hdi tim gid tri ciia cac thirc DS; phdn tich da thirc dn thda man ddng thdi moi thdnh nhdn tu, qui ddng mau phuang trinh ciia tap hgp do, sd cdc phan thirc; bien ddi ggi la mdt h | phuang tiinh; tijng ve eiia phugng trinh ve cdc gia tri cua cac an, thoa dang phil hgp vdi yeu cau ciia man ddng thdi mgi phuong trinh ciia he, la nghidm ciia bai toan de giai Ngay nhgn bai 20/8/2011 Ngay duy4l dang 25/10/2012 fi Vf dg: Phdn tich da thiic thdnh nhan tir Phan tich da thiic ihanh nhan tii cd the tien hanh theo cdc each nhu ddt thira si chung, nhdm cac hang tii, diing hdng ddng thiic dang nhd, phuang phdp tach cac hang tii, them bdt ciing mgt hang tir • TAP CHI THIET BI GIAO DUC - SO 87 -11/2012 NGHIEN CUU & UNG DUNG ht Hoat dgng gidi he phuang trinh cd nghia Id tim cdc gid tri cua cac an thda man ddng thdi mgi phuang trinh ciia he Vi du: Gidi phuang trinh bdc nhat mdt dn Be gidi phucmg trinh bdc nhat mdt dn ed the hudng ddn HS thyc hien thdng qua cdc budc sau: Vi dy: Gidi phucmg trinh: ( - l ) ^ ( - l ) H - | 1G DUNG - Xdc dinh ham sd thdng quadd thj ciia no, - Ve thi cua ham so; - Bieu dien sy tuong ung da cho dudi dgng dd thi; - Tir thi ham so suy mdt sd tinh chat ciia hdm so; - Sir dyng thi hdm so dc giai todn \'i d^: Dgy hgc khai nigm ham sd bgc nhat y = ax + b (a t 0) (Ldp 9) cd thl td chirc cho HS thyc hign thdng qua cdc hogt dgng sau: Hogl dgng !: Td chuc cho HS on tap bo sung kien thirc cii nhu: Dinh nghTa ve hdm sd; Cdc cdch xdc dinh hdm sd; Ki hieu ham sd va gia trj cua ham sd tai mgt diem; Dd thi eiia hdm sd y = fl^x); Hdm sd ddng bien, hdm sd nghjch bien Hogt dgng 2: Xdy dung kien thic mdi: Dinh nghTa ve hdm sd bdc nhat; Tinh chat ciia ham sd bac nhat; Dd thj ciia hdm sd bdc nhdt; He sd gde ciia dudng thdng y = ax + b; Vj tri tuong ddi ciia hai dudng thdng mat phdng Hogt dgng 3: Ciing cd kien thuc: Td chirc cho HS lam cac bdi tgp dgng: Tinh gia tri ciia hdm sd theo gia trj cua bien sd hay ngugc lai; Bieu dien cae diem (x; f(x)); Ve thj cua ham sd; Xdc djnh vj tri tucmg ddi cua hai dudng thdng 2.6- Hogt dgng van dting kiin thic SH vd DS vdo thuc tien Hoat d0ng van dung kien thlie SH vd DS (ndi rieng, ndi chung la kien thuc Toan hgc) vdo thyc tien thyc chat la sir dung cac kien thiic SH va DS Iam cdng cy d l giai quySt mgt 10 tinh hudng thyc tien Trong trudng hgp co Ih^, trinh bdy nhii'ng kien thirc todn hgc (khdi nigm, dinh li, qui t d c ) can CO gdng dan ddt HS bdng cac vi dy, tinh huong thyc te gan gui vdi ddi sdng ciia HS Dong thdi, sau xdy dyng xong mgt ngi dung kien thiic todn hgc, can cimg co bdng cdch dua cdc vi dy, tinh huong thyc tc phii hgp vdi kicn thlie todn hgc dd Vigc vgn dyng kien thirc Todn hgc vdo thyc tien ndi chung deu thyc hign theo qui trinh: Tinh hudng thyc tien —> md hinh hod todn hgc -> sir dyng phuang phdp toan hgc de gidi quyet —> dieu chinh ket qua cho phii hgp vdi tinh hudng ban dau Nhu vdy, dung trudc mgt tinh hudng thyc te, khdng phdi da cd bdi toan thyc te ma phai phat hign van de can giai quyet, nhihig dai Iugng tham gia vdo cdc mdi quan hg giua chiing Do vay, de td chiic cho HS thyc hign hogt dgng van dyng kien thiic Todn hgc vao thyc tien can chu y tdi mgt sd ngi dung sau: Td chiic cho HS thu nhgn nhChig thdng tin mang tinh chat Todn hgc tir nhung tinh hudng thyc tiln; Cho HS lien hg nhutig yeu td cua Toan hgc vdi nhiing yeu td thyc tien Viec td chiic cho HS vgn dyng kien thiic Toan hgc vdo thyc tidn phdi duge tien hanh d tdt cd cde khau cua qua trinh day hgc Cdc logi bdi len Idp khac nhu: bai len ldp li thuydt, bai luygn t$p, bai thyc hdrJi ddu cd the khai thac • TAP CHI THIET BI GIAO DUC-50 S7-11/2012 de rdn luygn v^n dyng kiln thuc Todn hgc vdo thyc tiln Day hgc SH vd DS trudng THCS theo hudng to chuc cac hogt dgng SH, DS Id hinh thirc to chiic dgy hgc md d dd GV xdy dyng cac tinh hudng su phgm de HS hoat dgng vd thdng qua hogt dgng dd de tiep nhgn tri thirc./ Tdi ligu tham khao Phan Due Chinh (Tdng chu bien), Todn 6, 7, 8, tap 1, 2, NXB Gido dye Pham Vdn Hoan, Tran Thiic Trinh, Nguyen Gia Coc, Gido due hgc mdn Todn, NXB Gido due, 1981 Nguyen Ky, Phuang phdp gido due tich cue, lay ngudi hgc ldm trung tdm NXB Gido due, 1995 Nguyen Canh Toan, Phuang phdp lugn vgt bifn chung vdi vifc hgc, dgy, nghien cihi todn hgc, tgp h tdp2,'NXB Dgi hgc Qudc gia, 1997 Trdn Anh Tudn, Dgy hgc mon Todn a trudng THCS Nhd xudt ban DHSP, 2007 Summary In this paper, we present concept of arithmetic and algebra activities We also give information about some types of arithmetic and algebra activities frequently used in secondary schools curriculum, accompi some examples ... due hgc mdn Todn, NXB Gido due, 1981 Nguyen Ky, Phuang phdp gido due tich cue, lay ngudi hgc ldm trung tdm NXB Gido due, 1995 Nguyen Canh Toan, Phuang phdp lugn vgt bifn chung vdi vifc hgc, dgy,