Question

18-(х-5)(х-4)=-2
Можно дискриминантом

Answer 1

18 - (x - 5)(x - 4) = -2

-(x² - 9x + 20) + 20 = 0

9x - x² = 0

x(9 - x) = 0

x₁ = 0        x₂ = 9

Ответ: {0; 9}

Answer 2

1
$18 - (x {}^{2} - 4x - 5x + 20) + 2 = 0 \\ 18 - x {}^{2} + 9x - 20 + 2 = 0 \\ - x {}^{2} + 9x = 0 \\ x {}^{2} - 9x = 0 \\ D=( - 9) {}^{2} - 4 \times 1 \times 0 = 81$
x1=(9-9)/2=0
x2=(9+9)/2=9