Chapter 5: Problem 9
Evaluate the given third-order determinants. $$\left|\begin{array}{rrr} 4 & -3 & -11 \\ -9 & 2 & -2 \\ 0 & 1 & -5 \end{array}\right|$$
Short Answer
Expert verified
The determinant is 202.
Step by step solution
01
Identify matrix elements
The matrix given is a 3x3 matrix:\[\begin{array}{rrr} 4 & -3 & -11 \ -9 & 2 & -2 \ 0 & 1 & -5 \end{array}\]The elements are straightforward to read from the matrix: the first row elements are 4, -3, -11; the second row elements are -9, 2, -2; and the third row elements are 0, 1, -5.
02
Use the formula for a 3x3 determinant
To calculate the determinant of a 3x3 matrix, use the formula: \[\text{Det} = a(ei-fh) - b(di-fg) + c(dh-eg)\]where the matrix elements are:\[\begin{array}{ccc} a & b & c \ d & e & f \ g & h & i \end{array}\]
03
Substitute the matrix elements into the determinant formula
Substitute the values from the matrix into the formula:\[a = 4, \, b = -3, \, c = -11, \ d = -9, \, e = 2, \, f = -2, \ g = 0, \, h = 1, \, i = -5\]The determinant expression becomes:\[4(2 \times (-5) - (-2) \times 1) - (-3)(-9 \times (-5) - (-2) \times 0) + (-11)(-9 \times 1 - 2 \times 0)\]
04
Perform the calculations inside parentheses
Now, simplify within the parentheses:\[4((-10) + 2) - (-3)((45) - 0) + (-11)((-9) - 0)\]This simplifies to:\[4(-8) - (-3)(45) + (-11)(-9)\]
05
Calculate the products
Calculate each term:\[4 \times (-8) = -32\]\[-3 \times 45 = -135\] (but because of the negative sign in front, it becomes +135)\[-11 \times (-9) = 99\]
06
Sum all the terms
Now combine all the terms:\[-32 + 135 + 99 = 202\]
07
Final result
After summing all terms, we find that the determinant of the matrix is 202.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding a 3x3 Matrix
A 3x3 matrix is an arrangement of numbers in three rows and three columns. In our example, the numbers in the matrix are organized as follows:
- First row: 4, -3, -11
- Second row: -9, 2, -2
- Third row: 0, 1, -5
Basics of Matrix Algebra
Matrix algebra involves the manipulation of matrices through operations such as addition, subtraction, and multiplication.
One task in matrix algebra is finding a determinant, a value that can provide a lot of information about the matrix itself.
When discussing a 3x3 matrix, matrix algebra uses elements arranged in rows and columns. Matrix operations are systematic and follow strict rules:
One task in matrix algebra is finding a determinant, a value that can provide a lot of information about the matrix itself.
When discussing a 3x3 matrix, matrix algebra uses elements arranged in rows and columns. Matrix operations are systematic and follow strict rules:
- Matrix addition and subtraction occur element-wise, which means you simply add or subtract corresponding elements from each matrix.
- Matrix multiplication, however, is more complex and requires taking the dot products of rows and columns.
Determinant Calculation for a 3x3 Matrix
The determinant of a 3x3 matrix is a special number calculated from its elements that can reveal important properties of the matrix.
The formula to find the determinant is:\[\text{Det} = a(ei - fh) - b(di - fg) + c(dh - eg)\]In simpler terms, this process involves selecting specific elements and calculating their products in structured steps:
The formula to find the determinant is:\[\text{Det} = a(ei - fh) - b(di - fg) + c(dh - eg)\]In simpler terms, this process involves selecting specific elements and calculating their products in structured steps:
- Products are formed using cross-multiplication of elements in rows and columns.
- Several subtractions and additions are executed according to the formula.
- The process involves lots of operations within parentheses first, then proceeding outward to complete the remaining calculation.