交点(3,0)
倾斜角2a
tan2a=k=4/3
tan2a=2tana/(1-tan²a)=4/3
2tan²a+3tana-2=0
显然a是锐角
所以tana>0
tana=1/2
即斜率是1/2,过(3,0)
x-2y-3=0