-5х+9(-1+2х)=9х-1
-5х-9+18х=9х-1
-5х+18х-9х=9-1
4х=8
х=8:4
х=2
-5x -9 +18x -9x +1=0
4x -8 = 0
x = 2
2x² - 7x - 9 < 0;
2x² - 7x - 9 = 0; D = 49 + 72 = 121; √D = 11; x₁ = (7 + 11)/4 = 4,5; x₁ = (7 - 11)/4 = -1.
Ответ: х ∈ (-1; 4,5)
Ответ: