# 3 x 3 determinant | Matrix transformations | Linear Algebra | Khan Academy | Summary and Q&A

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November 2, 2009
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3 x 3 determinant | Matrix transformations | Linear Algebra | Khan Academy

## TL;DR

Determinants are used to determine if a matrix has an inverse and can be computed using specific formulas.

## Key Insights

• โ The determinant of a matrix is used to determine if the matrix has an inverse.
• ๐ซ  The formula for the determinant of a 2x2 matrix is ad - bc.
• ๐ป The determinant of a 2x2 matrix is computed using specific entry combinations.
• ๐คจ The determinant of a 3x3 matrix is computed by expanding along the first row and recursively finding the determinant of submatrices.
• โ The determinant of a 3x3 matrix determines if the matrix is invertible.
• ๐ป The determinant of a 3x3 matrix can be computed using specific entry combinations.
• โ The determinant of a matrix is an important concept in linear algebra.

## Transcript

In the last video we defined the notion of a determinant of a 2 by 2 matrix. So if I have some matrix-- let's just call it B-- if my matrix B looks like this, if its entries are a, b, c, d, we've defined to determinant of B. Which could also be written as B with these lines around it, which could also be written as the entries of the matrix with th... Read More

### Q: What is the determinant of a 2x2 matrix?

The determinant of a 2x2 matrix is computed using the formula ad - bc.

### Q: How is the determinant related to finding the inverse of a matrix?

The determinant of a matrix is used to determine if the matrix has an inverse. If the determinant is not zero, the matrix is invertible.

### Q: How is the determinant of a 3x3 matrix computed?

The determinant of a 3x3 matrix is computed by expanding along the first row and recursively finding the determinant of the resulting 2x2 submatrices.

### Q: What does the determinant of a 3x3 matrix indicate?

The determinant of a 3x3 matrix determines if the matrix is invertible. If the determinant is not zero, the matrix is invertible.

## Summary & Key Takeaways

• An explanation of the determinant of a 2x2 matrix and its formula: ad - bc.

• The determinant of a 2x2 matrix determines if the matrix is invertible.

• Introduction to the determinant of a 3x3 matrix and its computation.