F.4 coordinate mathematics question

As follows~~~


圖片參考：http://i182.photobucket.com/albums/x4/A_Hepburn_1990/lines.jpg?t=1190372090

1.let L1 pass through A(2,-1)
slope of L1=(y+1)/(x-2)
slope of the line 4x+5y+6=0,=-4/5
since L1 perpendicular to 4x+5y+6=0,so the equation of line should be:
(y+1)/(x-2)x(-4/5)=-1
...........4y-5x+14=0

2.(y+1)/(x-2)=(y-3)/(x-0)
........y+2x-3=0

3.let (a,0) and (0,a) be the point on both axes
slope of that line=(a-0)/(0-a)=-1
the equation of the line:
(y+1)/(x-2)=-1
.......y+x-1=0

2007-09-21 19:43:02 補充：
樓上答得很工整,但個人認為最尾x 2y=0要rejected