急F4 Equations of Straight Line

30a) ∵L1 isa horizontal line∴Theequation of L1 is y=4The equationof L2 is y-0=[(4-0)/(3-0)](x-0)y=(4/3)x3y=4x4x-3y=0 b) ∵L3parallel to L2∴slope ofL3=L2∴Theequation of L3 isy-0=(4/3)(x-0)3y=4x4x-3y=0 31a) Theequation of L2 isy-0=2(x-0)y=2x2x-y=0 b) Let thecoordinates of Q be (x,-4)sub (x,-4)into equation of L22x-(-4)=02x=-4x=-2∴Q(-2,-4) c) Let thestraight line which passes through Q be L3∵L3 perpendicularto L2∴slope of L3= -1/2∴Theequation of L3 isy-(-4)=(-1/2)(x+2)2y+8=x+2x-2y-6=0

2011-09-09 18:09:07 補充：
30a) The equation of L2 is
y-4=[(4-0)/(3-0)](x-3)
y-4=(4/3)(x-3)
3y-12=4x-12
4x-3y=0

2011-09-09 18:09:54 補充：
30a) ∴The equation of L3 is
y-4=(4/3)(x-0)
3y-12=4x
4x-3y+12=0

2011-09-09 18:12:20 補充：
correct
30b) ∴The equation of L3 is
y-4=(4/3)(x-0)
3y-12=4x
4x-3y+12=0

2011-09-09 18:14:17 補充：
∴Theequation of L3 is

y-(-4)=(-1/2)(x+2)

2y+8=-x-2

x+2y+10=0