Решение на фото..........

1)

[tex]3 {x}^{2} - 12 = 0 \\ {x}^{2} - 4 = 0 \\ (x - 2)(x + 2) = 0 \\ x_{1} =2 \\ x _{2} = - 2[/tex]

2)

[tex]3 {x}^{2} + 7x = 0 \\ {x}^{2} + \frac{7}{3} x = 0 \\ x(x + 2 \frac{1}{3} ) = 0 \\ x_{1} = 0\\ x _{2} = - 2 \frac{1}{3} [/tex]