선형대수학

1

1.linear equations

how to read

linear equation of n equations in m unknowns

solutions

inconsistent

no solution

consistent

has solution

homogeneous system

trivial solution

nontrivial solution

?

equivalent system = infinitely many solutions 역도 가능?

unique solution

infinitely many solutions

equivalent system

a unique solution

infinitely many solutions

2.Matrix

definition

rectangular array of numbers

row ㅡ

column ㅣ

행렬 정의

vector

nx1 matrix

square matrix

m=n

main diagonal

Mmn

the set of all mxn matrices

A 부분집합 M

Matrix operation

matrix addition

scalar multiplication

linear combination

coefficient

transpose

multiplication

dot product

inner product

u•c=R

x•x>0

Matrix multiplication

matrix multiplication is not commutative

u•v=(u^t)v

matrix-vector product

Augmented matrix

3.properties matrix operation

matrix addition

commutative low

A+B=B+A

Associative low

A+(B+C)=(A+B)+C

zero matrix

0

matrix multiplication

associative properties

A(BC)=(AB)C

distributive property

(A+B)=AC+BC

C(A+B)=CA+CB

is not commutative

Ax=0 c1x1+c2x2 is also solution

transpose

(AB)^t

disprove

AB=0 , A=0 or B=0

AB=AC then B=C

AB=BC

4.special types of Matrices

diagonal matrix

square matrix

scalar matrix

identity matrix

A^p

A^0

(AB)^n 1

(AB)^n 2

triangular

upper triangular

lower triangular

symmetric

symmetric

skew symmetric

skew symmetric

2

5.Inverse Matrix

invertible - nonsingular

AB=BA=In

A,B square matrix AB=In BA is not in

properties

uniqueness

B=~~=C

(AB)^-1

A^-1)^-1

A^T)^-1

unique solution

6.vector(1)

Reflection

projection

Dilation and contraction

Rotation

counterclockwise rotation

counterclockwise rotation

7.Echelon Form

definition

condition of echelon form

1.all zero

2.leading one

3.to the right and below

4.column all zero

elementary row operations

row equivalent

row operations

finite number?

REF (row echelon form)

RREF(reduced row echelon form)

Gauss-Jordan reduction

contradiction

parameter

8.Determinant

definition

permutation

Inversion

even/odd

number of inversion

number of permutation

ex) 132=1

if det(A)=0 adj(A)= speicfic form?

ex (1 2 3, 0 2 2 , 1 4 5) adj(A)= (2 2 -2 , 2 2 -2 , -2 -2 0 )

A*B=0 B is a unique matrix?

theorem 3.1

how to get solution in linear algebra

1.row operation

  1. determinant

unique solution

A inverse

crammer rule

echelon form

reduced row operation

n!

properties

tranpose

all 0 row(column)

interchange row(column)

equal row(column)

scalar

row operation

triangular

I

inverse

product

Cofactor

Minor

I≠K 0