ПОЖАЛУЙСТА РЕШИТЕ СИСТЕМУ

$(x + 2y)(x - 2y) = 9 \\ y(x + 2y) = 3 \\ \\ \\ \\ (x + 2y)(x - 2y) = 9 \\ 3y(x + 2y) = 9 \\ \\ \\ 3y = x - 2y \\ \\ x = 5y \\ \\7y \times 3y = 9 \\ 21 {y}^{2} = 9 \\ {y}^{2} = \frac{9}{21} \\ \sqrt{ {y}^{2} } = \sqrt{ \frac{9}{21} } = \frac{3}{ \sqrt{21} } \\ |y| = \frac{3}{ \sqrt{21} } \\ y = + - \frac{3}{ \sqrt{21} } \\ \\ \\ x = + - \frac{15}{ \sqrt{21} } \\ \\$

Знаки либо - и - , либо + и +.