Vector is not a linear combination of two vectors [matrix algebra]

In summary, to find a vector w in R3 that is not a linear combination of v1 and v2, one can take the cross product of v1 and v2. This vector will be orthogonal to both v1 and v2 and therefore not within their span. However, any vector not spanned by v1 and v2 can be used as w.
  • #1
dlevanchuk
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Homework Statement


Find a vector w in R3 such that w is not a linear combination of v1 and v2


Homework Equations


v1 = [1;2;-1] v2=[2;-1;-2]


The Attempt at a Solution



my question is : does w need to be in the span of v1 and v2?? Could i just choose [1; 1; 1] as my w vector??
 
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  • #2
If w is NOT a linear combination of v1 and v2 then it CANNOT be in the span of v1 and v2.

An easy way of finding one such vector is to take the cross product of v1 and v2. The cross product of v1 and v2 is orthogonal to both v1 and v2 and is therefore not within the span of v1 and v2. But really, any vector not spanned by v1 and v2 is perfectly acceptable.
 
  • #3
that makes perfect sense! thank you
 

1. What does it mean when a vector is not a linear combination of two vectors?

When a vector is not a linear combination of two vectors, it means that the vector cannot be expressed as a linear combination of the two given vectors. In other words, the vector cannot be written as a sum of scalar multiples of the two vectors.

2. How can you determine if a vector is not a linear combination of two vectors?

To determine if a vector is not a linear combination of two vectors, you can use the process of elimination. If you cannot find any scalar multiples of the given vectors that can be added together to create the vector in question, then it is not a linear combination of the two vectors.

3. Why is it important to know if a vector is not a linear combination of two vectors?

Knowing if a vector is not a linear combination of two vectors is important because it tells us that the vector is not dependent on the two given vectors. This can help in solving systems of equations and understanding the relationships between vectors.

4. Can a vector be a linear combination of more than two vectors?

Yes, a vector can be a linear combination of more than two vectors. In fact, a vector can be a linear combination of any number of vectors, as long as the vectors are not linearly dependent.

5. How can matrix algebra be used to determine if a vector is not a linear combination of two vectors?

In matrix algebra, a system of equations can be represented using matrices and vectors. By setting up the system of equations and using row operations to reduce the matrix to its row echelon form, we can determine if a vector is not a linear combination of two vectors. If the reduced row echelon form has a row of zeros and the corresponding entry in the vector is non-zero, then the vector is not a linear combination of the two given vectors.

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