Kernel and images of linear operator, examples

In summary, the linear operator L(p(x)) = x*p'(x) has a kernel consisting of all x values where L(p'(x)) = 0, which can be solved by setting xp'(x) = 0. The range of this operator is the set of functions that can be obtained from L(p(x)), which in this case is the set of functions of the form 2ax^2 + bx, where a can be any real number.
  • #1
Niles
1,866
0

Homework Statement


If I e.g. want to find the kernel and range of the linear opertor on P_3:

L(p(x)) = x*p'(x),

then we can write this as L(p'(x)) = x*(2ax+b). What, and why, is the kernel and range of this operator?

The Attempt at a Solution


The kernel must be the x's where L(p'(x)) = 0, so do I just solve the equation?

The range is the elements that span the polynomial, so it is span{(x^2,x)}?

Hope you can help.
 
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  • #2
Niles said:

Homework Statement


If I e.g. want to find the kernel and range of the linear opertor on P_3:

L(p(x)) = x*p'(x),

then we can write this as L(p'(x)) = x*(2ax+b). What, and why, is the kernel and range of this operator?

The Attempt at a Solution


The kernel must be the x's where L(p'(x)) = 0, so do I just solve the equation?
Well, L(p)= 0, not L(p'). You must solve xp'(x)= 0 for all x.

The range is the elements that span the polynomial, so it is span{(x^2,x)}?
If every member of P_3 can be written as [itex]p(x)= ax^2+ bx+ c[/itex], then [itex]p'(x)= 2ax+ b[/itex] and so L(p(x))= [itex]2ax^2+ bx[/itex]. That set of functions is the range. Since a can be any number, so 2a can be any number.
 
  • #3
The kernel:
2ax^2+bx = 0 <=> 2ax+b=0 - is this the kernel, or do I have to isolate x first?

The range:
Ok, so the range is just the set of functions we get from L(p(x))?

I know these are quite basic subjects in linear algebra, but it is explained so poorely in my book and they've only spent ½ page giving definitions - nothing else.
 

1. What is the kernel of a linear operator?

The kernel of a linear operator is the set of all inputs that are mapped to the zero vector by the operator. In other words, it is the set of all vectors that when multiplied by the operator result in the zero vector.

2. What is the image of a linear operator?

The image of a linear operator is the set of all possible outputs that can be obtained by applying the operator to the input vectors. It is also known as the range of the operator.

3. Can you give an example of a linear operator?

Yes, one example of a linear operator is the transformation matrix used in a rotation or translation in 3D space. Another example is the differentiation operator in calculus.

4. How can the kernel and image of a linear operator be used in applications?

The kernel and image of a linear operator can be used to solve systems of linear equations, find eigenvalues and eigenvectors, and determine whether a linear transformation is invertible. They are also important in applications involving vector spaces, such as computer graphics and control systems.

5. Is the kernel and image of a linear operator always the same size?

No, the size of the kernel and image of a linear operator can vary depending on the dimensions of the input and output spaces. In general, the kernel and image can have different sizes, but the dimension of the image cannot be larger than the dimension of the input space.

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