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The linear transformation \(L\) defined by \\[ L(p(x))=p^{\prime}(x)+p(0) \\] \(\operatorname{maps} P_{3}\) into \(P_{2} .\) Find the matrix representation of \(L\) with respect to the ordered bases \(\left[x^{2}, x, 1\right]\) and \([2,1-x] .\) For each of the following vectors \(p(x)\) in \(P_{3},\) find the coordinates of \(L(p(x))\) with respect to the ordered basis \([2,1-x]\) (a) \(x^{2}+2 x-3\) (b) \(x^{2}+1\) (c) \(3 x\) (d) \(4 x^{2}+2 x\)

Short Answer

Expert verified
The matrix representation of the linear transformation L with respect to the ordered bases \(\{x^2, x, 1\}\) and \(\{2, 1-x\}\) is: \[ A = \begin{bmatrix} 0 & 1/2 & 0 \\ -2 & -1/2 & 0 \\ \end{bmatrix} \] The coordinates of L(p(x)) with respect to the ordered basis \(\{2, 1-x\}\) are: (a) \(L(x^{2}+2 x-3)= \frac{1}{2}(2) + \frac{-7}{2}(1-x)\) (b) \(L(x^{2}+1)= \frac{1}{2}(2) + \frac{-3}{2}(1-x)\) (c) \(L(3x)= \frac{3}{2}(2) + \frac{-3}{2}(1-x)\) (d) \(L(4x^{2}+ 2x)= 1(2) + (-8)(1-x)\)

Step by step solution

01

Find images of the basis elements under L

Let's find the images of the basis elements \(x^2, x\) and \(1\) under L. We have: i) \(L(x^2) = (x^2)'+ x^2(0) = 2x\) ii) \(L(x)= (x)' + (x)(0) = 1\) iii) \(L(1) = (1)' + (1)(0)= 0\)
02

Express the images in terms of the basis \(\{2, 1-x\}\)

Now, let's express the images of the basis elements found in Step 1 in terms of the basis \(\{2, 1-x\}\): i) The image of \(x^2\) under L is \(2x\). To express it in terms of \(\{2, 1-x\}\), we need to find the coefficients \(a\) and \(b\) such that \(2x = a(2) + b(1-x)\). From this equation, we have: \(a=0\) and \(b=-2\). So, \(2x = 0(2) + (-2)(1-x)\) ii) The image of \(x\) under L is \(1\). To express it in terms of \(\{2, 1-x\}\), we need to find the coefficients \(a\) and \(b\) such that \(1 = a(2) + b(1-x)\). From this equation, we have: \(a=\frac{1}{2}\) and \(b=-\frac{1}{2}\). So, \(1 = \frac{1}{2}(2) + ( -\frac{1}{2})(1-x)\) iii) The image of \(1\) under L is \(0\). Since \(0\) is a trivial linear combination, we have: \(0 = 0(2) + 0(1-x)\)
03

Construct the matrix representation of L

Now, we will construct the matrix representation of L using the coefficients found in Step 2. The matrix A representing L with respect to the given bases is: \[ A = \begin{bmatrix} 0 & 1/2 & 0 \\ -2 & -1/2 & 0 \\ \end{bmatrix} \]
04

Compute L(p(x)) for the given input polynomials

Now, we are ready to find the transformed polynomials for the given input polynomials in terms of the basis \(\{2, 1-x\}\): (a) \(L(x^{2}+2x-3)\): Reach the final answer using the matrix representation on \(p(x)= x^{2}+2x−3\) A[p(x)] = \[ \begin{bmatrix}0 & 1/2 & 0 \\ -2 & -1/2 & 0 \\\end{bmatrix} \begin{bmatrix}1 \\ 2 \\ -3 \\\end{bmatrix} = \begin{bmatrix}\frac{1}{2} \\ -\frac{7}{2} \\ \end{bmatrix}\] Therefore, \(L(x^{2}+2 x-3)= \frac{1}{2}(2) + \frac{-7}{2}(1-x)\) (b) \(L(x^{2}+1)\): Reach the final answer using the matrix representation on \(p(x)= x^{2}+1\) A[p(x)] = \[ \begin{bmatrix}0 & 1/2 & 0 \\ -2 & -1/2 & 0 \\\end{bmatrix} \begin{bmatrix}1 \\ 0 \\ 1 \\\end{bmatrix} = \begin{bmatrix}\frac{1}{2} \\ -\frac{3}{2} \\ \end{bmatrix}\] Therefore, \(L(x^{2}+1)= \frac{1}{2}(2) + \frac{-3}{2}(1-x)\) (c) \(L(3x)\): Reach the final answer using the matrix representation on \(p(x)= 3x\) A[p(x)] = \[ \begin{bmatrix}0 & 1/2 & 0 \\ -2 & -1/2 & 0 \\\end{bmatrix} \begin{bmatrix}0 \\ 3 \\ 0 \\\end{bmatrix} = \begin{bmatrix}\frac{3}{2} \\ -\frac{3}{2} \\ \end{bmatrix}\] Therefore, \(L(3x)= \frac{3}{2}(2) + \frac{-3}{2}(1-x)\) (d) \(L(4x^{2} + 2x)\): Reach the final answer using the matrix representation on \(p(x)= 4x^{2}+2x\) A[p(x)] = \[ \begin{bmatrix}0 & 1/2 & 0 \\ -2 & -1/2 & 0 \\\end{bmatrix} \begin{bmatrix}4 \\ 2 \\ 0 \\\end{bmatrix} = \begin{bmatrix}1 \\ -8 \\ \end{bmatrix}\] Therefore, \(L(4x^{2}+ 2x)= 1(2) + (-8)(1-x)\)

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Most popular questions from this chapter

Find the standard matrix representation for each of the following linear operators: (a) \(L\) is the linear operator that rotates each \(\mathbf{x}\) in \(\mathbb{R}^{2}\) by \(45^{\circ}\) in the clockwise direction. (b) \(L\) is the linear operator that reflects each vector \(\mathbf{x}\) in \(\mathbb{R}^{2}\) about the \(x_{1}\) -axis and then rotates it \(90^{\circ}\) in the counterclockwise direction. (c) \(L\) doubles the length of \(\mathbf{x}\) and then rotates it \(30^{\circ}\) in the counterclockwise direction. (d) \(L\) reflects each vector \(\mathbf{x}\) about the line \(x_{2}=x_{1}\) and then projects it onto the \(x_{1}\) -axis.

Let \(L\) be the operator on \(P_{3}\) defined by $$L(p(x))=x p^{\prime}(x)+p^{\prime \prime}(x)$$ (a) Find the matrix \(A\) representing \(L\) with respect to \(\left[1, x, x^{2}\right]\) (b) Find the matrix \(B\) representing \(L\) with respect to \(\left[1, x, 1+x^{2}\right]\) (c) Find the matrix \(S\) such that \(B=S^{-1} A S\). (d) If \(p(x)=a_{0}+a_{1} x+a_{2}\left(1+x^{2}\right),\) calculate \(L^{n}(p(x))\)

Let \(L\) be the linear operator on \(\mathbb{R}^{3}\) defined by \\[ L(\mathbf{x})=\left(\begin{array}{l} 2 x_{1}-x_{2}-x_{3} \\ 2 x_{2}-x_{1}-x_{3} \\ 2 x_{3}-x_{1}-x_{2} \end{array}\right) \\] Determine the standard matrix representation \(A\) of \(L,\) and use \(A\) to find \(L(\mathbf{x})\) for each of the following vectors x: (a) \(\mathbf{x}=(1,1,1)^{T}\) (b) \(\mathbf{x}=(2,1,1)^{T}\) (c) \(x=(-5,3,2)^{T}\)

Let \(L: V \rightarrow W\) be a linear transformation, and let \(T\) be a subspace of \(W\). The inverse image of \(T\) denoted \(L^{-1}(T),\) is defined by \\[ L^{-1}(T)=\\{\mathbf{v} \in V | L(\mathbf{v}) \in T\\} \\] Show that \(L^{-1}(T)\) is a subspace of \(V\)

A linear transformation \(L: V \rightarrow W\) is said to be one-to-one if \(L\left(\mathbf{v}_{1}\right)=L\left(\mathbf{v}_{2}\right)\) implies that \(\mathbf{v}_{1}=\mathbf{v}_{2}\) (i.e., no two distinct vectors \(\mathbf{v}_{1}, \mathbf{v}_{2}\) in \(V\) get mapped into the same vector \(\mathbf{w} \in W\) ). Show that \(L\) is oneto-one if and only if \(\operatorname{ker}(L)=\left\\{\mathbf{0}_{V}\right\\}\)

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