а) 2х^2+8х+15=0
б) 6х^2+х=0
в) 8-9х^2=0

2x² + 8x + 15 = 0
D/4 = 16 - 15 * 2 < 0
x ∉R

6x² + x = 0
x(6x + 1) = 0
x₁ = 0
6x + 1 = 0
6x = -1
x₂= -1/6
Ответ: -1/6; 0

8 - 9x² = 0
9x² = 8
x² = 8/9
x = ± √8/3 = ±2√3/3
Ответ: