1.过点（—1,3）,斜率为3
y-3=3(x+1)
y-3=3x+3
(1)y=3x+6
(2)y/6-x/2=1
2.过点（—3,1）（1,-5）
k=(-5-1)/(1+3)=-3/2
y-1=-3/2(x+3)
y-1=-3/2x-9/2
(1)y=-3/2x-7/2
(2)-x/(7/3)-y/(7/2)=1
3.过点（3,1）且与向量s=(2,3）平行
k=3/2
y-1=3/2(x-3)
y-1=3/2x-9/2
y=3/2x-7/2
x/(7/3)-y/(7/2)=1