8.4 Matrix Operations Day 1 Thurs May 7 Do Now Solve X – 2y = -6 3x + 4y = 7
Matrices A matrix is an organization of numbers in a rectangular form
Matrices The rows of a matrix are horizontal The columns are vertical A matrix with m rows and n columns is said to be of order m x n The numbers in a matrix are called entries The main diagonal starts from the top left and travels down and to the right
Matrix Operations Matrix Addition and Subtraction Scalar Multiplication Matrix Multiplication
Matrix Addition and Subtraction Given Matrix A and B with the same order A + B = add corresponding entries A – B = subtract corresponding entries
Ex Find A + B for
Ex Find C – D for
You try Find A + B for
Additive Inverse The additive inverse of a matrix is obtained by replacing each entry with its opposite
Ex Find –A and A + (-A) given
Scalar Multiplication The scalar product of a number k and a matrix A is the matrix kA, obtained by multiplying each entry of A by the number k
Ex Find 3A and (-1)A for
Ex P.716
Matrix Multiplication When multiplying 2 matrices, there is a prerequisite that must be satisfied, or it cannot happen Matrix: Dimensions: The two inside dimensions must be equal, or the multiplication is not defined Note: Just because AB exists, doesn’t mean that BA also exists
Can we multiply these matrices? 1) 2) 3)
Multiplying Matrices To multiply, take the 1st row of matrix A and the 1st column of Matrix B – Multiply each corresponding element, and then add them together to get each new element
Ex Let Find 1) AB 2) BA 3) BC 4) AC
Closure Multiply AB given HW: p.720 #1-27 odds
8.4 Matrix Operations Day 2 Fri May 8 Do Now Find AB given
HW Review: p.720 #1-27
Properties of Matrix Multiplication A(BC) = (AB)C A(B + C) = AB + AC (B + C)A = BA + CA Note that property 2 and 3 result in different matrices
Word problems When constructing a matrix from a word problem, the rows and columns should represent different types of the same thing (rows: types of cookies) (columns: amount of sugar)
Ex7 P.718
Matrix Equations We can write a system of equations into a matrix equation by making each column equivalent to a variable
Ex Write the following system into a matrix equation 4x + 2y – z = 3 9x + z = 5 4x + 5y – 2z = 1
Closure What must be true when multiplying matrices? Adding matrices? HW: p.720 #29-45 odds