Алгебра. Решить примеры:

1) = - 9x - 8

2) - 20x = - 5x - 13 -

X² = - 9x - 8

x² + 9x + 8 = 0

x² + 8x + x + 8 = 0

x (x+8) + x + 8 = 0

(x + 8) (x+1) = 0

x+8=0

x+1=0

x=-8

x=-1

x1=-8

x2=-1

2)

x² - 20x = - 5x - 13 - x²

x² - 20x + 5x + 13 + x² = 0

2x² - 15x + 13 = 0

2x² - 2x - 13x + 13 = 0

2x (x-1) - 13 (x - 1) = 0

(x-1) (2x - 13) = 0

x-1 = 0

2x - 13 = 0

x = 1

x = 13/2 = 6,5

x1 = 1

x2 = 6,5

1) x² = - 9x - 8; x² + 9x + 8 = 0; x₁ = 8; x₂ = 1. Ответ: 8; 1.

2) x² - 20x = - 5x - 13 - x²; x² + x² + 5x - 20x + 13 = 0; 2x² - 15x + 13 = 0;

D = b² - 4ac = 225 - 4·2·13 = 225 - 104 = 121; √D = 11;

x₁ = (15 + 11) / 4 = 6,5; x₂ = (15 - 11) / 4 = 1.

Ответ: 6,5; 1.