Ответ:
1) x²+5x-6=0
D=b²-4ac = 25-4 · 1 · (-6) = 25 + 4 · 6 = 49
x1 = (-b + √D)/(2a) = (-5 + 7)/2 = 2/2 = 1
х2 = (-b - √D)/(2a) = (-5 - 7)/2 = = -12/2 = -6
2) Зх²+2х-1=0
D=b²-4ac = 4 - 4 · 3 · (-1) = 4 + 12 = 16
x1 = (-b + √D)/(2a) = (-2 + 4)/(2 · 3) = 2/6 = 1\3
х2 = (-b - √D)/(2a) = (-2 - 4)/(2 · 3) = -6/6 = -1
Остальное аналогично