Solve {ccc}{-1}&{1}&{0}{1}&{2}&{4}{5}&{4}&{2}

$$\left| \begin{array} { c c c } { - 1 } & { 1 } & { 0 } \\ { 1 } & { 2 } & { 4 } \\ { 5 } & { 4 } & { 2 } \end{array} \right|$$

Evaluate

$$30$$

Steps Using Sarrus' Rule

Find the determinant of the matrix using the method of diagonals.

$$det(\left(\begin{matrix}-1&1&0\\1&2&4\\5&4&2\end{matrix}\right))$$

Extend the original matrix by repeating the first two columns as the fourth and fifth columns.

$$\left(\begin{matrix}-1&1&0&-1&1\\1&2&4&1&2\\5&4&2&5&4\end{matrix}\right)$$

Starting at the upper left entry, multiply down along the diagonals, and add the resulting products.

$$-2\times 2+4\times 5=16$$

Starting at the lower left entry, multiply up along the diagonals, and add the resulting products.

$$4\times 4\left(-1\right)+2=-14$$

Subtract the sum of the upward diagonal products from the sum of the downward diagonal products.

$$16-\left(-14\right)$$

Subtract -14 from 16.

$$30$$

Steps Using Expansion by Minors

Find the determinant of the matrix using the method of expansion by minors (also known as expansion by cofactors).

$$det(\left(\begin{matrix}-1&1&0\\1&2&4\\5&4&2\end{matrix}\right))$$

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.

$$-det(\left(\begin{matrix}2&4\\4&2\end{matrix}\right))-det(\left(\begin{matrix}1&4\\5&2\end{matrix}\right))$$

For the 2\times 2 matrix \left(\begin{matrix}a&b\\c&d\end{matrix}\right), the determinant is ad-bc.

$$-\left(2\times 2-4\times 4\right)-\left(2-5\times 4\right)$$

Simplify.

$$-\left(-12\right)-\left(-18\right)$$

Add the terms to obtain the final result.

$$30$$

Factor

$$2\times 3\times 5$$