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

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SUMMARY

The discussion focuses on demonstrating the equality of two 3x3 determinants without direct evaluation, as presented in Boas 3rd Edition, Chapter 3, Section 3, Question 7. The first determinant involves variables 'a', 'b', and 'c' with products in the third column, while the second determinant features squares of these variables. Key strategies discussed include manipulating rows by multiplication, extracting common factors from columns, and performing column interchanges while tracking sign changes in the determinant. These techniques lead to the conclusion that the two determinants are indeed equal.

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Homework Statement



Show without evaluating the determinant the equality.

Homework Equations

<br /> <br /> \left(<br /> \begin{array}{ccc}<br /> 1 &amp; a &amp; bc \\<br /> 1 &amp; b &amp; ac \\<br /> 1 &amp; c &amp; ab<br /> \end{array}<br /> \right)<br /> <br />

=

<br /> <br /> \left(<br /> \begin{array}{ccc}<br /> 1 &amp; a &amp; a^2 \\<br /> 1 &amp; b &amp; b^2 \\<br /> 1 &amp; c &amp; c^2<br /> \end{array}<br /> \right)<br /> <br />

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.
 
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(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.
 
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.
 

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