Chapter 3: Problem 56
Let \(M\) denote the set of \(2 \times 2\) matrices over \(\mathbf{w} .\) Let \(f : N \rightarrow M\) defined by \(f(n)=\left[\begin{array}{ll}{1} & {1} \\ {1} & {0}\end{array}\right]^{n} .\) Compute \(f(n)\) for each value of \(n.\) $$5$$
Short Answer
Expert verified
\(f(5) = \begin{bmatrix} 8 & 5 \\ 5 & 3 \end{bmatrix}\)
Step by step solution
01
Compute the square of the matrix #
First we need to compute the square of the matrix.
Calculate \(\begin{bmatrix}1 & 1 \\1 & 0\end{bmatrix}^2 = \begin{bmatrix}1 & 1 \\1 & 0\end{bmatrix} \begin{bmatrix}1 & 1 \\1 & 0\end{bmatrix}\).
$$
\begin{bmatrix}
1 \cdot 1 + 1 \cdot 1 & 1 \cdot 1 + 1 \cdot 0 \\
1 \cdot 1 + 0 \cdot 1 & 1 \cdot 1 + 0 \cdot 0
\end{bmatrix} = \begin{bmatrix} 2 & 1 \\ 1 & 1 \end{bmatrix}
$$
02
Compute the cube of the matrix #
Next we need to compute the cube of the matrix.
Calculate \(\begin{bmatrix}1 & 1 \\1 & 0\end{bmatrix}^3 = \begin{bmatrix}1 & 1 \\1 & 0\end{bmatrix} \begin{bmatrix}2 & 1 \\1 & 1\end{bmatrix}\).
$$
\begin{bmatrix}
1 \cdot 2 + 1 \cdot 1 & 1 \cdot 1 + 1 \cdot 1 \\
1 \cdot 2 + 0 \cdot 1 & 1 \cdot 1 + 0 \cdot 1
\end{bmatrix} = \begin{bmatrix} 3 & 2 \\ 2 & 1 \end{bmatrix}
$$
03
Compute the fourth power of the matrix #
Now we need to compute the fourth power of the matrix.
Calculate \(\begin{bmatrix}1 & 1 \\1 & 0\end{bmatrix}^4 = \begin{bmatrix}1 & 1 \\1 & 0\end{bmatrix} \begin{bmatrix}3 & 2 \\2 & 1\end{bmatrix}\).
$$
\begin{bmatrix}
1 \cdot 3 + 1 \cdot 2 & 1 \cdot 2 + 1 \cdot 1 \\
1 \cdot 3 + 0 \cdot 2 & 1 \cdot 2 + 0 \cdot 1
\end{bmatrix} = \begin{bmatrix} 5 & 3 \\ 3 & 2 \end{bmatrix}
$$
04
Compute the fifth power of the matrix #
Finally, we need to compute the fifth power of the matrix.
Calculate \(f(5) = \begin{bmatrix}1 & 1 \\1 & 0\end{bmatrix}^5 = \begin{bmatrix}1 & 1 \\1 & 0\end{bmatrix} \begin{bmatrix}5 & 3 \\3 & 2\end{bmatrix}\).
$$
\begin{bmatrix}
1 \cdot 5 + 1 \cdot 3 & 1 \cdot 3 + 1 \cdot 2 \\
1 \cdot 5 + 0 \cdot 3 & 1 \cdot 3 + 0 \cdot 2
\end{bmatrix} = \begin{bmatrix} 8 & 5 \\ 5 & 3 \end{bmatrix}
$$
So, \(f(5) = \begin{bmatrix} 8 & 5 \\ 5 & 3 \end{bmatrix}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
2x2 Matrices
In mathematics, a 2x2 matrix is a simple array consisting of two rows and two columns. The elements of a 2x2 matrix are usually represented as \(\begin{bmatrix}a & b\c & d\end{bmatrix}\).These matrices are essential in various calculations, including transformations and equations.
In the context of linear algebra, they are often used to describe transformations in a two-dimensional space.Some key features of 2x2 matrices include:
In the context of linear algebra, they are often used to describe transformations in a two-dimensional space.Some key features of 2x2 matrices include:
- Determinant: The determinant of a 2x2 matrix provides insights into the matrix's behavior, such as whether it is invertible. For a matrix \(\begin{bmatrix}a & b\c & d\end{bmatrix}\), the determinant is calculated as \(ad - bc\).
- Identity Matrix: This is a special kind of 2x2 matrix represented by \(\begin{bmatrix}1 & 0\0 & 1\end{bmatrix}\), which, when multiplied by another matrix, leaves it unchanged, like multiplying a number by 1.
- Zero Matrix: It consists solely of zeros, and multiplying any matrix by this matrix results in the zero matrix itself.
Matrix Multiplication
Matrix multiplication is a fundamental operation in linear algebra, essential for solving many mathematical problems, including those involving transformations and system equations.When dealing with 2x2 matrices, you need to perform element-wise multiplication and summation. Suppose you want to multiply two matrices, \(\begin{bmatrix}a & b\c & d\end{bmatrix}\)and \(\begin{bmatrix}e & f\g & h\end{bmatrix}\).The result is obtained as follows:
- Top-left element: \(a \cdot e + b \cdot g\)
- Top-right element: \(a \cdot f + b \cdot h\)
- Bottom-left element: \(c \cdot e + d \cdot g\)
- Bottom-right element: \(c \cdot f + d \cdot h\)
Linear Algebra
Linear algebra is a vital area of mathematics that deals with vector spaces, matrices, and linear transformations. It provides a framework for modeling and solving problems in science and engineering.
At its core, linear algebra revolves around:
- Vector Spaces: A collection of vectors where vector addition and scalar multiplication are defined. They form the basis for various linear models.
- Matrices: Key components in linear algebra used to transform vector spaces. They also represent linear transformations, which map one vector space to another.
- Eigenvalues and Eigenvectors: Concerns special vectors associated with a matrix that remain proportional to their original value after transformation by the matrix. They are crucial in stability analysis and quantum mechanics.
- Solving Linear Systems: Finding solutions to equations consisting of linear expressions.
- Transformations: Used in computer graphics for rotating, scaling, and translating objects.
- Machine Learning: Algorithms often rely on linear algebra, specifically in operations involving high-dimensional data.