笛卡兒坐標..

L1和L2的交點:
2x+3y-1=0...(1)
x+2y-3=0...(2)
(1)-2x(2)
2x-2x+3y-4y-1+6=0
-y+5=0
y=5...(3)
sub(3) into (1)
2x+3(5)-1=0
2x=-14
x=-7

so L1和L2的交點是(-7,5)
由於直線垂直L3..so 直線的斜率xL3的斜率=-1
m(L3):5x-2=-3y
y=-5/3x-2/3
m(L3)=-5/3
m(L)=(y-5)/(x+7)
(y-5)/(x+7) X (-5/3)=-1
-5(y-5)=-3(x+7)
-5y+25=-3x-21
3x-5y+46=0

直線之方程是 3x-5y+46=0