$$\left. \begin{array} { l } { 18.4 x ^ { 2 } + 4 b x - ( a ^ { 2 } - b ^ { 2 } ) = 0 } \\ { 19. a x ^ { 2 } + ( 4 a ^ { 2 } - 3 b ) x - 12 a b = 0 } \end{array} \right.$$
$x=-\frac{5\sqrt{\frac{368a^{2}-288b^{2}}{5}}}{184}-\frac{5b}{46}\text{, }y=19$
$x=\frac{5\sqrt{\frac{368a^{2}-288b^{2}}{5}}}{184}-\frac{5b}{46}\text{, }y=19$
$x=-\frac{5\sqrt{\frac{368a^{2}-288b^{2}}{5}}}{184}-\frac{5b}{46}\text{, }y=19$
$x=\frac{5\sqrt{\frac{368a^{2}-288b^{2}}{5}}}{184}-\frac{5b}{46}\text{, }y=19\text{, }|b|\leq \frac{\sqrt{46}|a|}{6}$
