1)X^2-6X+8=0 2)X^2+2X-8=0 3)X^2-2X-8=0 4)X^2+6X+8=0

Решим уравнения:

1) X^2 - 6 * X + 8 = 0;  

Найдем дискриминант квадратного уравнения. 

D = b^2 - 4 * a * c = 36 - 4 * 1 * 8 = 36 - 32 = 4; 

x1 = (6 + 4)/2 = 10/2 = 5;

x2 = (6 - 4)/2 = 2/2 = 1.

2) X^2 + 2 * X - 8 = 0; 

D = 4 - 4 * 1 * (-8) = 36;

x1 = (-2 + 6)/2 = 4/2 = 2;

x2 = (-2 - 6)/2 = -8/2 = -4.

3) X^2 - 2 * X - 8 = 0; 

D = 4 - 4 * 1 * (-8) = 36;

x1 = (2 + 6)/2  8/2 = 4;

x2 = (2 - 6)/2 = -4/2 = -2;

4) X^2 + 6 * X + 8 = 0; 

D = 36 - 4 * 1 * 8 = 36 - 32 = 4; 

x1 = (-6 + 4)/2 = -2/2 = -1; 

x2 = (-6 - 4)/2 = -10/2 = -5.