3a+2b=1 b = (1-3a )/2
所以 ax+by+2(x-y)-1=0
ax+y(1-3a)/2 + 2x-2y-1 = 0
a(2x-3y) + (4x-3y-2) = 0
令 2x-3y = 0
4x-3y-2 = 0
解出定点 (1,2/3)
3a+2b=1 b = (1-3a )/2
所以 ax+by+2(x-y)-1=0
ax+y(1-3a)/2 + 2x-2y-1 = 0
a(2x-3y) + (4x-3y-2) = 0
令 2x-3y = 0
4x-3y-2 = 0
解出定点 (1,2/3)