# Do Now: Solve each equation:

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Do Now: Solve each equation:

Workbook page 21 yes; 7 x ) yes; 2 x ) yes; 1 x 1 9) 11) )

Workbook page 21 19) 20) ) \$526,054

Determinants

**To find a determinant you must have a SQUARE MATRIX!!**
Determinant - a square array of numbers or variables enclosed between parallel vertical bars. **To find a determinant you must have a SQUARE MATRIX!!** Finding a 2 x 2 determinant:

Find the determinant:

Expansion by Minors Always:

Finding a 3x3 determinant: Expansion by Minors Method
6. Evaluate Step 1: Expand the matrix into 3 pieces. Step 2: Evaluate each 2x2 matrix. Step 3: Simplify. 21

Finding a 3x3 determinant: Diagonal method
Step 1: Rewrite first two columns of the matrix.

126 - (-52) 126 + 52 = 178 Step 2: multiply diagonals going up!
-224 +10 +162 = -52 Step 2: multiply diagonals going up! Step 2: multiply diagonals going down! +12 -126 +240 =126 Step 3: Bottom minus top! 126 - (-52) = 178

38 - 38 = 0 Step 2: multiply diagonals going up!
-18 +50 +6 = 38 Step 2: multiply diagonals going up! Step 2: multiply diagonals going down! - 15 45 + 8 = 38 Step 3: Bottom minus top! = 0

Do Now: Copy down this problem.
Find the area of a triangle whose vertices are located at (-1, 6), (2, 4), (0, 0).