There are several ways to find the value of a 3*3 determinant. One way to find the value of a determinant is to expand a determinant by minors. In general, the minor of an element in a 3*3 determinant is the 2*2 determinant that is found by eliminating the row and column that contain that element. The signs for the expansion of a 3*3 determinant by minors is The value of the determinant is the sum of the products of the elements in the choosen row and column, each with the appropriate sign and their minors. Example 1 You can expand by any row or column. We'll expand using elements in the second row and their minors. Sign of the element If we expand by third column we would get the following : Expansion by minor can be used with any determinant of order three or greater. Determinants can be used to solve systems of equations. To solve 3 equations and 3 unknowns the denominator for all three variables is the determinant of the coefficient of these variables which is a 3*3 determinant. For each variables numerator replace the coefficients for that variable with the constants on the right of the equations. Example2 We can substitute the value for x and y into any of the original equation to solve for z or we can evaluate the determinant. (Choosing the first equation)
Unit 7 Outline // Course Outline // Home Page
Copyright © 1996 by B. Chambers and P. Lowry. All Rights Reserved.