Linear Algebra: find a unique vector v given two other vectors related to v

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SUMMARY

The discussion focuses on finding a unique vector v given two vectors u=[1,1,-1] and w=[2,4,2] under specific conditions: v.u=1, v is orthogonal to w, |v|=sqrt(3), and v2 > 0. The solution involves using the equations v.u=v1+v2-v3=1 and |v|=sqrt(v1^2+v2^2+v3^2)=sqrt(3) to derive a quadratic equation for v2. The final step requires selecting the positive solution for v2 and substituting it back to find v1 and v3.

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Homework Statement


Let u=[1,1,-1] and w=[2,4,2].
Find the unique vector v=[v1,v2,v3] such that:
v.u=1
v is orthogonal to w
|v|=sqrt(3)
v2 > 0


Homework Equations


v.u=|v||u|cos(theta)


The Attempt at a Solution


I've just been blindly solving different aspects of this, but have no idea how to put it all together.

w.v=0

u.w=4

v.u=v1+v2-v3=1

|v|=sqrt(3) = sqrt(v1^2+v2^2+v3^2) therefore v1^2+v2^2+v3^2 = 3

cos(theta) between u and v is 1/3

cos(theta) between w and v is 1/sqrt(6)
 
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Never mind, I figured it out. You solve for v1 and v3 using the above relations, then plus both of those into v1^2+v2^2+v3^2 = 3 to get a quadratic only using v2.
The solve for v2 (only the positive answer) which you sub into any equation to find v1 and v3.
 

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