3x-4y-13=0与直线3x-4y+7=0之间距离=4l截得的线段为4倍根2所以,l与平行线夹角=π/4,3x-4y-13=0斜率为3/4设l斜率为k则：k=(3/4+tanπ/4) / (1-3/4*tanπ/4)=(3/4+1)/(1-3/4)=7或,k=(3/4+tan3π/4) / (1-3/4*tan3π/4)...