8x^2+x-75=0

3x^2-11x-14=0

3x^2+11x-34=0

8x² + x - 75 = 0

D = 1 + 4·75·8 = 2401 = 49²

x₁ = (-1 + 49) / 16 = 48/16 = 3

x₂ = (-1 - 49) / 16 = - 50/16 = - 25/8

Ответ: x = - 25/8; 3.

3x² - 11x - 14 = 0

D = 121 + 14·4·3 = 289 = 17²

x₁ = (11 + 17) / 6 = 28/6 = 14/3

x₂ = (11 - 17) / 6 = - 6/6 = - 1

Ответ: x = - 1; 14/3.

3x² + 11x - 34 = 0

D = 121 + 4·3·34 = 529 = 23²

x₁ = (-11 + 23) / 6 = 12/6 = 2

x₂ = (-11 - 23) / 6 = - 34/6 = - 17/3

Ответ: x = - 17/3; 2.