2:58T00 23 == | CH 17, 1EP a. Step 1/8 The main objective is to show that 0 -{(5) с or not. Step 2/8 | b,c,de R (R, +, .) Recall that multiplication are closed. is a subring of { * b 0 A = 1- (0₂5). B = ( ) = S C d " Let can be proved as follows. .25% ال... (0) is a Ring so, addition and < M₂ (R) then the result

Advanced Engineering Mathematics
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Chapter2: Second-order Linear Odes
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Why is it A-B. Isn't it A+B, since it is closes under addition. Please explain 

### CH 17, 1EP

**Step 1/8**

**Objective:**
The main goal is to determine if the set 

\[
S = \left\{ \begin{pmatrix} 0 & b \\ c & d \end{pmatrix} \mid b, c, d \in \mathbb{R} \right\}
\]

is a subring of \( M_2(\mathbb{R}) \).

**Step 2/8**

**Background:**
Recall that \( (\mathbb{R}, +, \cdot) \) is a ring, meaning addition and multiplication are closed within it.

Consider matrices:

\[
A = \begin{pmatrix} 0 & b \\ c & d \end{pmatrix}, \quad B = \begin{pmatrix} 0 & e \\ f & g \end{pmatrix} \in S
\]

To test for subring properties, perform the following operations:

1. **Matrix Subtraction:**

   \[
   A - B = \begin{pmatrix} 0 & b - e \\ c - f & d - g \end{pmatrix}
   \]

2. **Matrix Multiplication:**

   \[
   AB = \begin{pmatrix} b \cdot f & b \cdot g \\ d \cdot f & c \cdot e + d \cdot g \end{pmatrix}
   \]

For \( AB \) to remain in \( S \), the element at position (1,1) must be 0. However, if \( b, f \neq 0 \), this condition is not satisfied (\( b \cdot f \neq 0 \)), thus \( AB \notin S \).

**Conclusion:**
Therefore, 

\[
S = \left\{ \begin{pmatrix} 0 & b \\ c & d \end{pmatrix} \mid b, c, d \in \mathbb{R} \right\}
\]

is not a subring of \( M_2(\mathbb{R}) \).
Transcribed Image Text:### CH 17, 1EP **Step 1/8** **Objective:** The main goal is to determine if the set \[ S = \left\{ \begin{pmatrix} 0 & b \\ c & d \end{pmatrix} \mid b, c, d \in \mathbb{R} \right\} \] is a subring of \( M_2(\mathbb{R}) \). **Step 2/8** **Background:** Recall that \( (\mathbb{R}, +, \cdot) \) is a ring, meaning addition and multiplication are closed within it. Consider matrices: \[ A = \begin{pmatrix} 0 & b \\ c & d \end{pmatrix}, \quad B = \begin{pmatrix} 0 & e \\ f & g \end{pmatrix} \in S \] To test for subring properties, perform the following operations: 1. **Matrix Subtraction:** \[ A - B = \begin{pmatrix} 0 & b - e \\ c - f & d - g \end{pmatrix} \] 2. **Matrix Multiplication:** \[ AB = \begin{pmatrix} b \cdot f & b \cdot g \\ d \cdot f & c \cdot e + d \cdot g \end{pmatrix} \] For \( AB \) to remain in \( S \), the element at position (1,1) must be 0. However, if \( b, f \neq 0 \), this condition is not satisfied (\( b \cdot f \neq 0 \)), thus \( AB \notin S \). **Conclusion:** Therefore, \[ S = \left\{ \begin{pmatrix} 0 & b \\ c & d \end{pmatrix} \mid b, c, d \in \mathbb{R} \right\} \] is not a subring of \( M_2(\mathbb{R}) \).
Expert Solution
Step 1: Given a subset S of 2×2 matrices over reals

To check: S is a subring or not

steps

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