ax + by = c ... 1
dx + ey = f ... 2
由1得 x = (c - by) / a 代入2
[d(c - by)] / a + ey = f
=> (dc - bdy) / a + ey = f
=> dc - bdy + aey = af
=> aey - bdy = af - dc
所以 y = (af - dc) / (ae - bd)
x 也是使用同樣的方法~~