3x−2y+4z=0 Any vector w=⎣⎡xyz⎦⎤ in W satisfies 3x−2y+4z=0 or equivalently x=32y−34z.
Thus we have
w=⎣⎡xyz⎦⎤=⎣⎡32y−34zyz⎦⎤=y⎣⎡2/310⎦⎤+z⎣⎡−4/301⎦⎤ Let
u1=⎣⎡2/310⎦⎤,u2=⎣⎡−4/301⎦⎤The above computation shows that any vector w in W can be written as a linear combination of the vectors u1,u2.
Hence the set {u1,u2} is a spanning set for the subspace W.
We claim that {u1,u2} is a linearly independent set.
Consider
a1u1+a2u2=0 The equation can be written as
⎣⎡(2/3)a1−(4/3)a2a1a2⎦⎤=⎣⎡000⎦⎤Comparing entries, we obtain a1=a2=0.
Thus the equation a1u1+a2u2=0 has only the zero solution and hence the vectors u1,u2
are linearly independent.
We found a basis
{u1=⎣⎡2/310⎦⎤,u2=⎣⎡−4/301⎦⎤}.
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