Đáp án:
a,
$$\left \{ {{3x - 2y=3} \atop {-2x+y=4}} \right.$$
`->` $$\left \{ {{3x - 2y =3} \atop {-4x+2y=8}} \right.$$
`->` $$\left \{ {{x=-11} \atop {3x - 2y=3}} \right.$$
`->` $$\left \{ {{x=-11} \atop {y=-18}} \right.$$
b,
$$\left \{ {{ax-2y=a} \atop {-4x + 2y = 2a+2}} \right.$$
`->` $$\left \{ {{ax-4x=3a+2} \atop {ax-2y=a}} \right.$$
`->` $$\left \{ {{x = \dfrac{3a + 2}{a-4}} \atop {y=\dfrac{a(x-1)}{2}}} \right.$$
`->` $$\left \{ {{x=\dfrac{3a + 2}{a-4}} \atop {y=\dfrac{a(\dfrac{3a + 2}{a-4}-1)}{2}}} \right.$$
