Question

2,4,6 помогите пожалуйста​

Answer 1

х^2 - 7х + 12 = 0

D = b^2 - 4ac

D = (- 7)^2 - 4 × 1 × 12 = 49 - 48 = 1

x = (- b ± √D)/2a

x = (-(-7) ± √1)/(2 * 1) = (7 ± 1)/2 = 4; 3

х^2 + 8х + 7 = 0

D = 8^2 - 4 × 1 × 7 = 64 - 28 = 36

х = (-8 ± √36)/(2 * 1) = (- 8 ± 6)/2 = - 7; - 1

х^2 + 2х - 15 = 0

D = 2^2 - 4 × 1 × (-15) = 4 + 60 = 64

x = (-2 ± √64)/(2 * 1) = (- 2 ± 8)/2 = - 5; 3

Answer 2

2) x² - 7x + 12 = 0

x₁ = 3       x₂ = 4    так как  3 + 4 = 7 ,    3 * 4 = 12

4) x² + 8x + 7 = 0

x₁ = - 1      x₂ = - 7   так как   - 1 - 7 = - 8 ,    - 1 * (- 7) = 7

6) x² + 2x - 15 = 0  

x₁ = - 5      x₂ = 3     так как   - 5 + 3 = - 2 ,      - 5 * 3 = - 15