# Intersection of two planes HELP

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#1
Would anyone be able to help with this question? I've tried it a few times but had a different answer every time

"Find an equation of the line of the intersection of the planes x + y − z = 0 and 2x − 5y − z = 1"
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3 weeks ago
#2
(Original post by ezrxtvghj)
Would anyone be able to help with this question? I've tried it a few times but had a different answer every time

"Find an equation of the line of the intersection of the planes x + y − z = 0 and 2x − 5y − z = 1"

If you used two different methods, it's possible that your two answers represent the same line, and both are valid.
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#3
(Original post by ghostwalker)

If you used two different methods, it's possible that your two answers represent the same line, and both are valid.
0
3 weeks ago
#4
(Original post by ezrxtvghj)
In your second image - quoted here - where did the third line come from: z+y=(1+z+5y)/2

Should be z-y, if I read it correctly.
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#5
(Original post by ghostwalker)
In your second image - quoted here - where did the third line come from: z+y=(1+z+5y)/2

Should be z-y, if I read it correctly.
oh yeah! must've read it wrong, so if I change a few things and the equations end up being x=1+6t, y=t and z=1+7t would that be correct?
0
3 weeks ago
#6
(Original post by ezrxtvghj)
oh yeah! must've read it wrong, so if I change a few things and the equations end up being x=1+6t, y=t and z=1+7t would that be correct?
Agreed.
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#7
(Original post by ghostwalker)
Agreed.
thank you so much for the help!
1
3 weeks ago
#8
(Original post by ezrxtvghj)
thank you so much for the help!
I presume you're happy with the fact that your two equations represent the same line.

For the benefit of others:
Direction vectors are scalar multples of each other, and:
Set the parameter for the line equal to 0 in each parameterisation to get two points, and check that one minus the other is a multiple of either of the direction vectors.
Last edited by ghostwalker; 3 weeks ago
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