3x^2+4x-39=0
D = 16 -4×3×(-39) = 16 + 468 = 484 > 0
x1 = -4+22 / 6 = 3
x2 = -4-22 / 6 = -26 / 6 = -4 2/6 = -4 1/3
Ответ: 3; -4 1/3.
4x^2-3x-1=0
D = 9 -4×4×(-1) = 9 + 16 = 25 > 0
x1 = 3+5 / 8 = 1
x2 = 3-5 / 8 = -2 / 8 = -1/4 = -0,25
Ответ: 1; -0,25.
3x^2+8x+5=0
D = 64 - 4×3×5 = 64 - 60 = 4 > 0
x1 = -8+2 / 6 = -1
x2 = -8-2 / 6 = -10/6 = -5/3 = - 1 2/3
Ответ: -1; -1 2/3.