III. PHAN PHOI THCJI LUONG
a)Bat phi/dng trinh bae nhat hai an va mien nghiem cua no
• GV neu dinh nghia.
• Bdt phuang trinh bdc nhdt hai dn Id bdt phuang trinh cd mot
ax + by + c < 0, ax + by + c> 0, ax + by + c < 0, ax + by + c > 0
2 2
trong dd a, b vd c Id cdc sd cho trudc sao cho a +b ^0;xvdy Id cdc dn.
• Mdi cap sd (XQ ; yg) sao cho axo+ byg + c < 0 /a mot bdt ddng
thitc diing ggi Id mot nghiem ciia bdt phuang trinh ax + by + c < 0.
Sau dd GV neu cac khai niem: - Mien nghiem.
- Bieu dien mien nghiem tren mat phing toa do.
b) Cach xac djnh mien nghiem cua bat phtrcfng trinh bae nhat hai an. • GV neu dinh li
Trong mat phdng toa do, mdi dudng thdng (d) .• ax + by + c = 0 chia mat phdng thdnh hai nita mat phdng. Mdt trong hai nita mat phdng dy (khdng ke bd (d)) gdm cdc diem cd toa do thoa mdn bdt phuang trinh ax + by + c > 0, /7f'to mat phdng kia (khdng ke bd (d)) gdm cdc diem cd toa do thoa mdn bdt phuang trinh ax + by + c < 0.
• GV neu each xac dinh mien nghiem
Ne'u (XQ ; yg) Id mdt nghiem cua bdt phuang trinh ax + by + c > 0 (hay ax + by + c < 0) thi nita mat phdng (khdng ke bd (d)) chita diem M(xo ; yo) chinh Id mien nghiem cua bdt phuang trinh dy.
• GV ggi HS neu ra cac budc sau:
- Ve dudng thing (d): ax + by + c = 0.
- Xet mdt diem M(xo, y„) khdng nim tren (d).
Ne'u axg + by^^ + c < 0 thi nira mat phing chiia diem M la mien nghiem ciia bit phuang trinh ax + by + c<0.
Neu ax,) + ^y,, + c > 0 thi nira mat phing khdng chiia diem M la mien nghiem ciia
bat phuang trinh da cho. * • GV neu chu y.: Hudng din HS khi nao tap nghiem lay ca bd.
• Neu vi du 1. 98
Sau dd GV dat cac cau hdi sau de thuc hien.
HI. Hay ve dudng thing cd phuong trinh: 3x + y = 0
H2. Hay chgn mdt dien thudc mdt trong hai nita mat phing.
H3. Thay vao phuong trinh dudng thing va xet xem diem dd cd thogc mien nghiem ciia bat phuong trinh hay khdng?
H4. Hay xac dinh tap nghiem ciia bat phuang trinh. Thuc hien H1
Xac dinh mien nghiem cua bat phuong trinh x + y > 0.
Hoat ddng ciia GV Cau hdi 1
Hay ve dudng thang x + y = 0
Cau hdi 2
Diem (0 ; 1) cd la nghiem cua bat phuang trinh khdng?
Cau hdi 3 (adsbygoogle = window.adsbygoogle || []).push({});
Xac dinh mi6n nghiem ciia bat phuong trinh -3.v + 2.v > 0
GV : Ggi 3 HS trd Idi ba cdu.
Hoat ddng cua HS
Ggi y tra Idi cau hdi 1
Dudng phan giac ciia gdc phan
II.
Ggi y tra Idi cau hdi 2
Diem (0 ; 1) la nghiem.
Goi y tra Idi cau hdi
tu
Mien chiia diem (0 : 1) la mien nghiem.
HOAT DONG 2