WUPS: Find the determinates by hand Name: _____________ WUPS: Find the determinates by hand 1. 3.8 Warm-ups 2. Corrected By: ______________________________
4.5 Use Inverse Matrices to Solve Matrix Equations By the end you should: 1. find the inverse of a 2 x 2 and 3 x 3 matrix 2. solve a matrix equation Identity Matrix: a square matrix (n x n) with 1's as its main diagonal and zeros everywhere else. 2 x 2 IM If a matrix is multiplied by an identity matrix, then you will get the matrix. Similar to multiplying a number by one. 3 x 3 IM
Inverse Matrices 1) 2 matrices are inverses of each other if their product (in both orders) equals the identity matrix. ex. AB = I and BA = I a matrix can only have an inverse if it is square its determinant does not equal zero (Remember: you may NEVER divide by 0)
Inverse of a 2x2 Matrix The Inverse of matrix is
….to find the inverse of a matrix (2 x 2) Let’s try some:
….to find the inverse of a 3 x 3 matrix using your calculator On your calculator….. Enter the 3 x 3 matrix Select matrix from the home screen Press ENTER What do you get?
Solve a Matrix Equation How would you normally solve for x? AX = B When you have a matrix you cannot “divide” by a matrix, so you take the ________________.
Your turn: solve the matrix equation
Solve a Linear System Solve the following linear system: 2x – 3y = 19 Step 1: write as a matrix equation AX = B coefficient · matrix of = matrix of matrix (A) variables (X) constants (B) Step 2: find the inverse of A Step 3: solve for X
Your turn: 1. -2x + 3y = -11 5x + y = 19 2. 4x + y = 10 3x + 5y = -1 Calculator: Enter A and B Your turn: 1. -2x + 3y = -11 5x + y = 19 2. 4x + y = 10 3x + 5y = -1 3. –x – 2y + 4z = -28 x + y + 2z = -11 2x + y – 3z = 30
Yeah….more word problems! At a video store, the cost of 3 DVDs, 2 video games, and 4 VHS movies is $130. The cost of 2 DVDs, 1 video game, and 5 VHS movies is $105. The cost of 3 DVDs, 3 video games, and 3 VHS movies is $135. Find the cost of each item.
…you must be able to solve by hand!!! Homework: 3.8 pg. 214 (3-29 odd, 35-37, 44) **** Do #3-11 SOLVE BY HAND Show ALL your work Beware... …you must be able to solve by hand!!!
Find the inverse BY HAND Exit Card 3.8 Name: ________________________ Find the inverse BY HAND Solve the system of linear equations using matrices 3x – 2y = 5 6x – 5y = 14