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Math 120 SP08
Test #2 Review: 3.1 – 3.3, 3.5, 6.1 – 6.4
Brodnick
3.1: Matrix Addition and Scalar Multiplication
*
columns
and
rows
has
matrix
n
m
n
m
×
*
3
column
and
1
row
in
matrix
in
entry
the
to
refers
3
1
A
a
*when adding or subtracting two matrices (of the same dimension), add or subtract corresponding entries
*when multiplying a matrix by a scalar, multiply each entry in the matrix by the scalar
*when computing the transpose of a matrix, the 1
st
row becomes the 1
st
column, 2
nd
row becomes the 2
nd
column, etc.
3.2: Matrix Multiplication
*in order to multiply two matrices, the “middle numbers” of their dimensions must be equal, and the dimensions of the matrix that
results are the “outside two numbers” of the two matrices (product of a 2×3 and a 3×4 will be a 2×4 matrix)
*when multiplying matrices by hand, take each row in the first matrix with each column in the second matrix – multiply each pair of
numbers and add them up
*identity matrix
I
: a square matrix with 1s down the diagonal and 0s everywhere else
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This note was uploaded on 04/07/2008 for the course MAT 120 taught by Professor Brodnick during the Spring '08 term at Illinois State.
 Spring '08
 Brodnick
 Math, Addition, Multiplication, Scalar

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