- #1
HizzleT
- 15
- 5
Homework Statement
How do I find a basis for:
the subspace of R^3 consisting of all vectors x such that x ⋅ (1,2,3) = 0.
Homework Equations
I believe this is performed through setting x = x,y,z, setting each parameter sequentially equal to 1 while the others are set to o, putting into a matrix where a^i --> v(subscript i), and transforming into row reduced echelon form.
The Attempt at a Solution
I believe I have done this correctly, but please tell me if I have not.
x ⋅ (1,2,3) = 0.
(x,y,z) ⋅ (1,2,3) = 0.
x + 2y + 3z = o
x = -2y -3z
that is,
x = -2s - 3t
y = s
z = t
Giving: (-2s-3t,s,t)
Set s = 1, t = 0
(-2,1,0)
Set s = 0, t = 1
(-3,0,1)
-2 -3
1 0
0 1
ROW REDUCTION
yields:
1 0
0 1
0 0
Transforming v1 and v2 into the elementary columns. Thus,
{(-2,1,0),(-3,0,1)} form a basis for the subspace of R^3 consisting of all vectors x such that x ⋅ (1,2,3) = 0.
DimS = 2
_____
If it is of any assistance, the answer in the back of the textbook is:
{(-2,1,0),(-3,0,1)} with dimS = 2
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