Determinant Equality Explained without Evaluation | Boas 3rd Ed. HW Question 7

In summary, the conversation is about how to show the equality of two matrices without evaluating the determinant. The suggested approach is to use facts about determinants and perform operations such as multiplying rows and taking out common factors to get the desired result. The importance of using the correct notation, specifically vertical lines for determinants, is also mentioned.
  • #1
iamthegelo
53
0

Homework Statement



Show without evaluating the determinant the equality.

Homework Equations

[itex]

\left(
\begin{array}{ccc}
1 & a & bc \\
1 & b & ac \\
1 & c & ab
\end{array}
\right)

[/itex]

=

[itex]

\left(
\begin{array}{ccc}
1 & a & a^2 \\
1 & b & b^2 \\
1 & c & c^2
\end{array}
\right)

[/itex]

The Attempt at a Solution



I tried the facts of determinants - I did column 3 plus column 2. I can't see it. This is actually a Question on Boas 3rd Ed. Chapter 3 Section 3 No. 7.
 
Last edited:
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  • #2
(The brackets that you are using is generally used for matrices; for a determinant, vertical lines are used to enclose it.)

Multiply the first row by 'a' and get 1/a outside. The 1st row becomes |a a^2 abc|. Now think what you can multiply the 2nd and 3rd rows with.

After that, take out something common from a column.

Then interchange columns or do a cyclic permutation on the columns, keeping track of the sign of the determinant. You will get the answer.

For any help, don't hesitate to ask.
 
  • #3
Shooting Star said:
(The brackets that you are using is generally used for matrices; for a determinant, vertical lines are used to enclose it.)

Multiply the first row by 'a' and get 1/a outside. The 1st row becomes |a a^2 abc|. Now think what you can multiply the 2nd and 3rd rows with.

After that, take out something common from a column.

Then interchange columns or do a cyclic permutation on the columns, keeping track of the sign of the determinant. You will get the answer.

For any help, don't hesitate to ask.

Yeah, I actually just copied and pasted that from somewhere here that I searched for, sorry, I don't know LATEX. Thanks, I will try your suggestion.
 

1. What is a determinant?

A determinant is a mathematical property that is used to determine the unique solution of a system of linear equations. It is a numerical value that is calculated from the coefficients of the equations.

2. How is a determinant calculated?

A determinant can be calculated using various methods such as the cofactor expansion method or the Gaussian elimination method. The most common method is the cofactor expansion method which involves multiplying the elements of a row or column by their corresponding minors and then adding or subtracting the resulting values.

3. What are some properties of determinants?

Some properties of determinants include linearity, which means that the determinant of a sum of matrices is equal to the sum of their determinants, and scalar multiplication, which means that multiplying a matrix by a constant also multiplies its determinant by that constant.

4. How is a determinant used in real life?

Determinants have many practical applications, especially in fields such as physics, engineering, and economics. In physics, determinants are used to solve systems of equations that represent physical laws. In engineering, determinants are used to calculate the stability and strength of structures. In economics, they are used to solve problems related to supply and demand.

5. Can determinants have negative or zero values?

Yes, determinants can have negative or zero values. The value of a determinant depends on the arrangement of the elements within a matrix, so it is possible for it to be negative or zero depending on the specific matrix. However, the absolute value of a determinant is always positive.

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