Question

Помогите пожалуйста. 1. (4x – 3)² - 2x(8x – 7) =111 2.(2x – 3)² - 4x(x – 3)=9 3.(x – 5)² - (x – 3)(x + 3) = 8 4.(8x+7)/2 +12x = 3(x – 1) 5.8(5x - 2)(4x+3) = 0

Answer 1

Ответ:

1)

(4x+1)(x-3)=12.

4х²+ х - 12х - 3 = 12

4х² - 11х - 15 = 0

D = b² - 4ac

D = 11² - 4 * 4 * (-15)=121+ 240 = 361

√D = √361 = 19

x₁ = (11+19)/(2*4) = 30/8=3,75

x₂ = (11-19)/(2*4) = -8/8= - 1 

 Ответ: - 1; 3,75

2)

(x+2)(x-3)-(2x-5)(x+3)=x(x-5) 

x²- 3x + 2x - 6 - 2x² + 5x - 6x + 15 = x² - 5x

- 2x² + 3x + 9 = 0 

D = b² - 4ac

D = 3² - 4 * (-2) * 9 = 9 + 72 = 81

√D = √81 = 9

x₁ = (-3+9)/(-2*2) = 6/(-4)= -1,5

x₂ =(-3-9)/(-2*2) = -12/(-4)= 3 

Ответ: -1,5; 3.