1) х 2 – 6х + 2 = 0 a = 1; b = - 6; c = 2
D = b 2 – 4ac
D =(- 6) 2 – 4 · 1 · 2 = 36 – 8 = 28 > 0 (2 корня)
2) 3х 2 + 8х – 1 = 0
a = 3; b = 8; c = -1
D = b 2 – 4ac
D =8 2 – 4 · 3 · (-1) = 64 + 12 = 76 > 0 (2 корня)
3) – х 2 + 8х + 3 = 0
a = - 1; b = 8; c = 3
D = b 2 – 4ac
D =8 2 – 4 · (-1) · 3 = 64 + 12 = 76 > 0 (2 корня)
4) х 2 – 10х + 25 = 0
a = 1; b = - 10; c = 25
D = b 2 – 4ac
D =(-10) 2 – 4 · 1 · 25 = 100 - 100 = 0 (1 корень)
5) 2х 2 – х - = 0
a = 2; b = - 1; c = -
D = b 2 – 4ac
D =(- 1) 2 – 4 · 2 · (-) = 1 + = > 0 (2 корня)
6) х 2 + 16х + 64 = 0
a = 1; b = 16; c = 64
D = b 2 – 4ac
D =16 2 – 4 · 1 · 64 = 256 - 256 = 0 (1 корень)
Стр. 66 № 7.2
1) 3х 2 – 12х – 9 = 0
a = 3; b = - 12; c = - 9
D = b 2 – 4ac
D =(- 12) 2 – 4 · 3 · ( - 9) = 144 + 108 = 252
2) - х 2 – 12х + 21 = 0
a = - 1; b = - 12; c = 21
D = b 2 – 4ac
D =(- 12) 2 – 4 · (- 1) · 21 = 144 + 84 = 228