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Evaluate the given determinants. $$\left|\begin{array}{cc} -20 & -15 \\ -8 & -6 \end{array}\right|$$

Short Answer

Expert verified
The determinant of the matrix is 0.

Step by step solution

01

Identify the Formula for a 2x2 Determinant

The determinant of a 2x2 matrix \( \left| \begin{array}{cc} a & b \ c & d \end{array} \right| \) is calculated using the formula: \[ ad - bc \] where \( a, b, c, \) and \( d \) are the elements of the matrix.
02

Assign Variables to the Matrix Elements

Assign the corresponding variables to the elements of the given matrix:\( a = -20, b = -15, c = -8, d = -6 \).
03

Calculate the Products

Using the variables assigned, first calculate the product of \( a \) and \( d \):\( ad = (-20) \times (-6) = 120 \).Next, calculate the product of \( b \) and \( c \):\( bc = (-15) \times (-8) = 120 \).
04

Substitute into the Formula and Simplify

Substitute the products into the determinant formula:\[ ad - bc = 120 - 120 \]Simplify this expression to find the determinant's value.
05

Evaluate the Determinant Value

Complete the calculation:\[ 120 - 120 = 0 \]The determinant of the given matrix is 0.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Determinant Calculation
The concept of the determinant calculation for a 2x2 matrix is a foundational element in linear algebra. It revolves around the straightforward formula: \[ ad - bc \]This formula allows you to find something called the 'determinant' of a matrix. The determinant provides valuable information about a matrix, such as whether it is invertible. In the context of a 2x2 matrix, the calculation is relatively simple:
  • The elements of the matrix are identified and labeled as \( a, b, c, \) and \( d \).
  • Multiplication of these elements in the pattern \( ad \) and \( bc \) is executed.
  • The final step is to subtract the second product from the first: \( ad - bc \).
This process ultimately yields a single numeric value, which can tell you a lot about the properties of the matrix.
Matrix Algebra
Matrix algebra is a fascinating area of mathematics that deals with operations on matrices—arrays of numbers arranged in rows and columns.
A 2x2 matrix has two rows and two columns, making it one of the simplest matrices to work with. Common operations include addition, subtraction, and, as relevant here, finding the determinant. The determinant, in particular, can help determine whether a matrix is invertible and influences the matrix's transformation properties. In the matrix:\[\begin{array}{cc}-20 & -15 \-8 & -6\end{array}\]
  • The determinant tells us if there are solutions present in a system of equations that the matrix might represent.
  • If the determinant is zero, as in this case, the matrix is considered singular and does not have an inverse.
Remembering the impact of the determinant on a matrix’s properties helps to understand broader applications in systems of linear equations and vector spaces.
Mathematical Steps
Let's break down the mathematical steps involved in calculating a determinant to deepen understanding:
1. **Identify Elements**: For our given matrix, these elements are\( a = -20 \), \( b = -15 \), \( c = -8 \), and \( d = -6 \). Recognizing each element correctly is the first important step.
2. **Compute Products**: Multiply the elements diagonally, first \( a \) by \( d \) and then \( b \) by \( c \):
- \( ad = (-20) \times (-6) = 120 \) - \( bc = (-15) \times (-8) = 120 \)
3. **Apply the Formula**: Substitute these products into the formula \( ad - bc \):
- \( 120 - 120 \)
4. **Evaluate and Conclude**: Simplifying this gives \( 0 \), thus concluding that the determinant equals zero.
By following these precise steps, even complex mathematical procedures become manageable. Breaking it down assures clarity and fortifies knowledge in matrix operations.

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Most popular questions from this chapter

Solve the given systems of equations by the method of elimination by addition or subtraction. $$\begin{aligned} &R-4 r=17\\\ &4 r+3 R=3 \end{aligned}$$

Solve the given problems by determinants. In a laboratory experiment to measure the acceleration of an object, the distances traveled by the object were recorded for three different time intervals. These data led to the following equations: $$\begin{array}{l} s_{0}+2 v_{0}+2 a=20 \\ s_{0}+4 v_{0}+8 a=54 \\ s_{0}+6 v_{0}+18 a=104 \end{array}$$ Here, \(s_{0}\) is the initial displacement (in \(\mathrm{ft}\) ), \(v_{0}\) is the initial velocity (in \(\mathrm{ft} / \mathrm{s})\), and \(a\) is the acceleration (in \(\mathrm{ft} / \mathrm{s}^{2}\) ). Find \(s_{0}, v_{0},\) and \(a\).

Solve the given systems of equations by the method of elimination by substitution. $$\begin{aligned} &6 s+6 t=3\\\ &4 s-2 t=17 \end{aligned}$$

Solve the given systems of equations by either method of this section. $$\begin{aligned} &15 x+10 y=11\\\ &20 x-25 y=7 \end{aligned}$$

Solve the given problems by determinants. In Exerciser-46,\( set up appropriate systems of equations. All numbers are accurate to at least two significant digits. An online retailer requires three different size containers to package its products for shipment. The costs of these containers, \)A, B\( and \)C,\( and their capacities are shown as follows: $$\begin{array}{lccc} \text { Container } & A & B & C \\ \text { cost (\)\$$ each) } & 4 & 6 & 7 \\ \text { Capacity (in. }^{3} \text { ) } & 200 & 400 & 600 \end{array}$$ If the retailer orders 2500 containers with a total capacity of \(1.1 \times 10^{6}\) in. \(^{3}\) at a cost of \(\$ 15,000,\) how many of each are in the order?

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