-4k+b=9 (1)
6k+b=3 (2)
(1)-(2)得:
-10k=6
k=-3/5 代入(2)得:
6×(-3/5)+b=3
-18/5+b=3
b=3+18/5=33/5 (并不是b=-33/5)
所有k=-3/5,b=33/5