Determine an equation of the line of intersection of the planes 5x+y+2z+15=0 and 2x+y+2z+8=0.

Answers is equation = (-7,20,0)+t(0,-2,1)

Question

Determine an equation of the line of intersection of the planes 5x+y+2z+15=0 and 2x+y+2z+8=0.

Answers is equation = (-7,20,0)+t(0,-2,1)

anonymous · Answer

I know how to find the direction vector (0,-2,1) but what about the point?

amistre64 · Answer

5x+y+2z+15 = 2x+y+2z+8

  5x +y +2z +15
-2x  -y  -2z  -8
-----------------
 3x               + 7 = 0

amistre64 · Answer

x = -7/3 seems to be the line of intersection if i did it right

amistre64 · Answer

i dont think I did it right :)

anonymous · Answer

oh lol

anonymous · Answer

yeah i figured it out

anonymous · Answer

First we find the direction vector by crossing the normals of each line

amistre64 · Answer

sounds good

anonymous · Answer

then we can find a point that is on both lines by finding a  point that satisfies both equation

anonymous · Answer

im sure you probably knew all this :P

anonymous · Answer

medal still for you pops :D

amistre64 · Answer

its rattling around up there someplace inbetween the rafters lol

anonymous · Answer

lol .. highschool ?

amistre64 · Answer

nah..... high school went and gone many many years ago

anonymous · Answer

lol .. PhD?

anonymous · Answer

:P