设l的斜率为k,则其方程为y = kx +1（点斜式）
kx - y+1 = 0
点（1,-3）到l的距离为|k*1 -(-3) + 1|/√(k² + 1) = 3√2/2
|k+4|/(k² + 1) = 3√2/2
7k² -16k -23 = 0
(7k - 23)(k+1) = 0
k1 = 23/7,y = 23x/7 + 1
k2 = -1,y = -x + 1