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det(\left(\begin{matrix}1&0&-4\\0&4&5\\2&5&13\end{matrix}\right))
Find the determinant of the matrix using the method of diagonals.
\left(\begin{matrix}1&0&-4&1&0\\0&4&5&0&4\\2&5&13&2&5\end{matrix}\right)
Extend the original matrix by repeating the first two columns as the fourth and fifth columns.
4\times 13=52
Starting at the upper left entry, multiply down along the diagonals, and add the resulting products.
2\times 4\left(-4\right)+5\times 5=-7
Starting at the lower left entry, multiply up along the diagonals, and add the resulting products.
52-\left(-7\right)
Subtract the sum of the upward diagonal products from the sum of the downward diagonal products.
59
Subtract -7 from 52.
det(\left(\begin{matrix}1&0&-4\\0&4&5\\2&5&13\end{matrix}\right))
Find the determinant of the matrix using the method of expansion by minors (also known as expansion by cofactors).
det(\left(\begin{matrix}4&5\\5&13\end{matrix}\right))-4det(\left(\begin{matrix}0&4\\2&5\end{matrix}\right))
To expand by minors, multiply each element of the first row by its minor, which is the determinant of the 2\times 2 matrix created by deleting the row and column containing that element, then multiply by the element's position sign.
4\times 13-5\times 5-4\left(-2\times 4\right)
For the 2\times 2 matrix \left(\begin{matrix}a&b\\c&d\end{matrix}\right), the determinant is ad-bc.
27-4\left(-8\right)
Simplify.
59
Add the terms to obtain the final result.