290 Expanding this determinant about the the second column....

In summary, the value of 32 (red) comes from the -8 and 4 in the original matrix. The second column in the expanded equation shows that the value is equal to (-8)(4) = -32. There is a possibility of encountering more questions on this example. Despite the views of curiosity, it seems that not many people can provide assistance with Linear Algebra problems. The individual asking for help also mentioned being confused with another problem.
  • #1
karush
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where does 32 (red) come from ?
nevermind looks its (-8)(4)=-32

but will probable have more ? on this example
 

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  • #2
Expanding on the second column we have
$\left|\begin{array}{ccc}\lambda- 5 & 0 & 4 \\ -12 & \lambda- 1 & 12 \\ -8 & 0 & \lambda- 7\end{array}\right|$$= -(\lambda- 1)\left|\begin{array}{cc} \lambda- 5 & 4 \\ -8 & \lambda+ 7 \end{array}\right|$$= -(\lambda- 1)[(\lambda- 5)(\lambda+ 7)- (-8)(4)]$$=-(\lambda- 1)[(\lambda- 5)(\lambda+ 7)+ 32]$.
The "32" comes from the -8 and 4 in the original matrix.
 
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  • #3
thank you for helping
I am getting the impression not to many here can help with Linear Algebra
despite all the views of curiosity :cool:I did this with another problem but was kinda :confused: with it

https://www.physicsforums.com/attachments/8909
 
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What is a determinant?

A determinant is a mathematical concept used to calculate properties of a square matrix, such as its invertibility and eigenvalues.

Why is the determinant important in mathematics?

The determinant plays a crucial role in various areas of mathematics, including linear algebra, differential equations, and geometry. It is used to solve systems of linear equations, determine the volume of a parallelepiped, and find the area of a triangle.

What does it mean to expand a determinant?

Expanding a determinant means to rewrite it as a sum of simpler determinants by using a specific set of rules, such as the Laplace expansion or the cofactor expansion. This allows us to solve for the value of the determinant more easily.

How do you expand a determinant about a specific column?

To expand a determinant about a specific column, we use the cofactor expansion method. This involves multiplying each element in the chosen column by its corresponding cofactor, and then summing the resulting determinants.

Can expanding a determinant about a different column change its value?

No, expanding a determinant about a different column does not change its value. The value of the determinant remains the same regardless of which column or row we choose to expand it about.

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