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: Linear Algebra: Describe the intersection of the two hyperplanes x1 + 2x2  x3 + x4 = 8 and x1 + 3x2 + x3  x4 = 2.
 2 years ago
 2 years ago
: Linear Algebra: Describe the intersection of the two hyperplanes x1 + 2x2  x3 + x4 = 8 and x1 + 3x2 + x3  x4 = 2.
 2 years ago
 2 years ago

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victoraranaBest ResponseYou've already chosen the best response.0
They intersecate on a plane
 2 years ago

windsylphBest ResponseYou've already chosen the best response.0
Is there a way to get an equation for that plane?
 2 years ago

tdabboudBest ResponseYou've already chosen the best response.0
You could set up the augmented matrix, row reduce to get the values and that should be the point of intersection
 2 years ago

windsylphBest ResponseYou've already chosen the best response.0
yep I did that.. and haha seemingly im stuck on a dumb question: let a and b be free variables. my solution then is (ab+4, 2, a, b)^T. How do I express that as a span, then as an equation?
 2 years ago

tdabboudBest ResponseYou've already chosen the best response.0
i get x2 = 2; x3 = x1 + x4  4; So like you said x1 and x4 are free so the span is: =(2 , 4) + x1(1, 0, 1, 0) + x4(0, 0, 1, 1) (these are vertical vectors I just cant write it on here) =(2, 4) + x1u + x4v (u and v are vectors above)
 2 years ago

tdabboudBest ResponseYou've already chosen the best response.0
I made a small mistake: It is x3 and x4 that are free so it becomes x1=4 +x3  x4 x2 =2 which translates to... =(2 , 4) + x3(1, 0, 1, 0) + x4(1, 0, 0, 1)
 2 years ago

windsylphBest ResponseYou've already chosen the best response.0
thanks, i was looking for an answer of the form span(u,v), but if that's that then that's okay. how about an equation for the plane?
 2 years ago

tdabboudBest ResponseYou've already chosen the best response.0
well span(u,v) is just the span of those vectors: span{ (1, 0, 1, 0) , (1, 0, 0, 1)}
 2 years ago

windsylphBest ResponseYou've already chosen the best response.0
oh, so (4,2,0,0)^T doesn't matter when expressing it in that form?
 2 years ago

tdabboudBest ResponseYou've already chosen the best response.0
nope because it only depends on the free variables
 2 years ago

windsylphBest ResponseYou've already chosen the best response.0
okay thanks. is there a way to express that as an equation?
 2 years ago
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