Cam nhan phuong trinh toan 8

Bai viet cua tui yeu cau ban im lang doc that cham...ca khi da hieu…
(***) Hi hi…bai nay jup cac ban lop 8 hieu them doi chut ve phuong trinh.cai tu phuong trinh thoat tien thi nghe hoi la mot chut nhung cac ban da tung lam ma khong biet.khi cac ban giai cac bai toan do lop 3,cac ban da su dung on so rui thiet lap he thuc sau do tim ra an so.o day he thuc do hay hai dang thuc duoc noi voi nhau boi dau “=” nguoi ta goi la “phuong trinh” va cac an so goi la bien “bien” va gia tri cua bien goi la nghiem cua phuong trinh.mot bai toan do co the rat nhieu an len ta co phuong mot an,hai an…o day ta chi xet phong trinh mot an “vi co n an thi phai co n phuong trinh lien he.tru phuong trinh nguyen”
(***) Phuong trinh co ban nhat la phuong trinh bac mot.phuong trinh bac mot la phuong trinh co an cao nhat la mot tuc chua x.phuong trinh co dang :ax+b=0.de ton tai x trong thuong trinh thi a#o .cach jai phuong trinh nay nhu sau :chuyen b sang ve ben kia :ax=-b.vi a#o len ta chia ca hai ve cua phuong trinh cho a.ta duoc : x=-b/a.don jan dung khong cac ban.cu nghi moi thu deu don jan di hi hi…cac ban thu lam mot vai vi du coi:
vd1.gpt: 15 – 8x = 9 – 5x ~ 15-9=8x-5x ~ 6=3x ~ x=2.vay pt co nghiem:x=2
vd2.gpt: 5 – (x – 6) = 4(3 – 2x) ~ 5-x+6=12-8x ~ 8x-x=12-6-5 ~ 7x=1 ~x=1/7 .vay pt co nghiem:x=1/7
Cac bai toan nay cac ban can luu y khi chuyen ve phai can than khong nham la ok.cac bai toan nay deu di tim he so a,b cua phuong trinh ax+b=0,rui cho x=-b/a.trong bai toan tren viec tim a,b that la don gian,nhung co mot so bai thi tim that kho.ta khong the tim theo cach thong dung,nhom tat ca cac thua so chua x de tim a,va cac thua so khong chua x de tim b duoc,ta thu coi vi du nay:
vd3.gpt:
.giai theo cach thong thuong ta se lam nhu sau:
, den day ta dem wy dong no xe ra mot so rat to.neu bai toan khong cho cac so 2003,2003,2004 , ma cho cac so to gap nhieu lan thi sao ta khong the lam theo cach nay duoc.ta se lam nhu sau:ta di tim dai luong y nao do thoa man:y=ax+b va phuong trinh tro thanh :y.hangso=khong.suy ra y=0 “day goi la phuong trinh tich.trinh tich la phuong trinh gom tich cac da thuc nhan voi nhau bang 0 suy ra mot trong cac da thuc phai bang khong”.suy ra x=-b/a.do do ta lam bai nay nhu sau :
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(***) nhu da noi o tren thi : y=-x+2004 va hang so bang
no co gia tri bao nhieu ta khong wan tam.viec jai bai toan nay ta su dung mot so bien doi tuong duong chung ta da hoc,de rui chung ta duoc phuong trinh bac nhat:y=ax+b=0.nguoi ta goi cach giai nay la wy ve phuong trinh bac nhat va cung co rat nhieu phuong trinh can chung ta wy ve phuong trinh bac nhat.tui gioi thieu vai loai sau day “nhung phuong trinh nay dung cac cach bien doi cac ban da hoc de wy ve chi mot so loai co ban nhat thui”cac ban len thuoc vi toan hoc can kinh nghiem la chinh “chung ta dang hoc khong phai nghien cuu len khong can tim cac cach jai moi la,dai dong mat thoi gian”.cu the nhu sau:
(***)Phuong trinh bac cao “lon hon 2”wy ve phuong trinh bac nhat:
1.phuong trinh bac 2:dang

Phuong trinh nay co ba truong hop xay ra tuy vao ve so a,b,c :
Truong hop 1:phuong trinh co nghiem “thuong la nghiem chan” cac ban phan tich se duoc 2 nhan tu “phuong trinh tich”rui ta suy ra duoc hai nghiem.cac ban se thac mac neu nghiem le thi sao “tui tra loi rang da la bai thi phai nghiem chan vi nghiem le cac ban chua hoc khong ai cho vuot wa truong trinh dung khong” tui lam vi du nhu sau :
vd4gpt :

truong hop 2:phuong trinh dua duoc ve dang hang dang thuc hay