6x^2+18x=0 x^2-8x+7=0 9x^2-4=0 через дискриминант

1) 6x(x +3) =0
6x =0, x =0
x +3 =0, x= -3

2) x² -8x +7 =0
D=64 -28 =36=6²
x1=(8 -6) /2 =1
x2=(8 +6) /2 =7

3) 9x² -4 =0
(3x -2)(3x +2) =0
3x -2 =0, 3x =2, x =2/3
3x +2 =0, 3x= -2, x= -2/3