Coordinates relative to a basis (linear algebra)

In summary, the set B = {-4-x^2, -8+4x-2x^2, -14+12x-4x^2} is a basis for P2 and the coordinates of p(x) = (-2 +0x -x^2) relative to this basis are c = <-5/2, 1, 12>T.
  • #1
hocuspocus102
45
0

Homework Statement


The set B = {-4-x^2, -8+4x-2x^2, -14+12x-4x^2} is a basis for P2. Find the coordinates of p(x) = (-2 +0x -x^2) relative to this basis.


Homework Equations


n/a


The Attempt at a Solution


so the set would be in a matrix like this:
|-4 0 -1|
|-8 4 -2|
|-14 12 -4| and multiplying this by

|-2|
| 0|
|-1| as the vector for p(x) gives

| 9|
|18|
|32| but that's not the right answer and I thought that's how you'd do it.
 
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  • #2
hocuspocus102 said:

Homework Statement


The set B = {-4-x^2, -8+4x-2x^2, -14+12x-4x^2} is a basis for P2. Find the coordinates of p(x) = (-2 +0x -x^2) relative to this basis.


Homework Equations


n/a


The Attempt at a Solution


so the set would be in a matrix like this:
|-4 0 -1|
|-8 4 -2|
|-14 12 -4| and multiplying this by

|-2|
| 0|
|-1| as the vector for p(x) gives

| 9|
|18|
|32| but that's not the right answer and I thought that's how you'd do it.
You're going at this the wrong way around. You want the vector c = <c1, c2, c3>T such that Ac = <-2, 0, -1>T, where A is the matrix you have above.
 
  • #3
oh ok, so if multiply A inverse times <-2, 0, -1> would it be right? I tried that and got <-5/2, 1, 12> which I checked but is still the wrong answer. Did I just put the coordinates in the wrong order or something? because the inverse thing makes sense but it didn't accept my answer. thanks.
 
  • #4
Those aren't the right coordinates. The coordinates I got check.
 
  • #5
oh ok, I figured it out, thanks a lot!
 

1. What are coordinates relative to a basis in linear algebra?

In linear algebra, coordinates relative to a basis refer to a system used to represent a vector or point in a multi-dimensional space. It involves expressing the vector or point in terms of a set of basis vectors that span the space.

2. Why are coordinates relative to a basis important in linear algebra?

Coordinates relative to a basis are essential in linear algebra because they allow us to represent and manipulate vectors and points in a multi-dimensional space in a more efficient and organized manner. It also helps in solving systems of linear equations and performing transformations on vectors and points.

3. What is the difference between a basis and a coordinate system?

A basis refers to a set of linearly independent vectors that span a vector space, while a coordinate system is a way of assigning numbers or coordinates to vectors in that space. In other words, a basis serves as the building blocks for a coordinate system.

4. How do you find coordinates relative to a basis?

To find coordinates relative to a basis, you need to express the vector or point as a linear combination of the basis vectors. This involves finding the coefficients or weights for each basis vector that, when multiplied with the basis vector, will result in the original vector or point.

5. Can coordinates relative to a basis be negative?

Yes, coordinates relative to a basis can be negative. The coordinates represent the distance or magnitude of the vector in each direction, so they can be positive, negative, or zero depending on the direction and length of the vector.

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