Đáp án:

$ \left\{\begin{array}{l} x=\dfrac{21-2\sqrt{7}}{3\sqrt{5}-6} \\ y=\dfrac{15-2\sqrt{7}+3\sqrt{5}}{2(\sqrt{5}-2)}\end{array} \right.$

Giải thích các bước giải:

$b)\left\{\begin{array}{l} 3\sqrt{5}x-4y=15-2\sqrt{7} \\ 3x-2y=-3\end{array} \right.\\ \Leftrightarrow \left\{\begin{array}{l} 3\sqrt{5}x-4y=15-2\sqrt{7} \\ -6x+4y=6\end{array} \right.\\ \Leftrightarrow \left\{\begin{array}{l} 3\sqrt{5}x-6x=21-2\sqrt{7} \\ -6x+4y=6\end{array} \right.\\ \Leftrightarrow \left\{\begin{array}{l} x=\dfrac{21-2\sqrt{7}}{3\sqrt{5}-6} \\ 4y=6x+6\end{array} \right.\\ \Leftrightarrow \left\{\begin{array}{l} x=\dfrac{21-2\sqrt{7}}{3\sqrt{5}-6} \\ y=\dfrac{3}{2}\left(\dfrac{21-2\sqrt{7}}{3\sqrt{5}-6} +1\right)\end{array} \right.\\ \Leftrightarrow \left\{\begin{array}{l} x=\dfrac{21-2\sqrt{7}}{3\sqrt{5}-6} \\ y=\dfrac{3(15-2\sqrt{7}+3\sqrt{5})}{2(3\sqrt{5}-6)}\end{array} \right.\\ \Leftrightarrow \left\{\begin{array}{l} x=\dfrac{21-2\sqrt{7}}{3\sqrt{5}-6} \\ y=\dfrac{15-2\sqrt{7}+3\sqrt{5}}{2(\sqrt{5}-2)}\end{array} \right.$