- #1
JNBirDy
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Homework Statement
i) Find all vectors v such that <1,2,1> X v = <3,1,-5>
ii) Explain why there is no vector v such that <1,2,1> X v = <3,1,5>
Homework Equations
a X b = <a[itex]_{2}[/itex]b[itex]_{3}[/itex] - a[itex]_{3}[/itex]b[itex]_{2}[/itex], a[itex]_{3}[/itex]b[itex]_{1}[/itex] - a[itex]_{1}[/itex]b[itex]_{3}[/itex], a[itex]_{1}[/itex]b[itex]_{2}[/itex] - a[itex]_{2}[/itex]b[itex]_{1}[/itex])
The Attempt at a Solution
i)
<1,2,1> X v
= <2v[itex]_{3}[/itex] -v[itex]_{2}[/itex], v[itex]_{1}[/itex] - v[itex]_{3}[/itex], v[itex]_{2}[/itex] - 2v[itex]_{1}[/itex]>
Which leaves me with three equations:
2v[itex]_{3}[/itex] -v[itex]_{2}[/itex] = 3
v[itex]_{1}[/itex] - v[itex]_{3}[/itex] = 1
v[itex]_{2}[/itex] - 2v[itex]_{1}[/itex] = -5
Now, every time I try to fiddle with them, I end up with 0 = 0.
Any help?