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Chapter 1
Theorems, definitions, and proofs
10
Mathematics
02/16/2012

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Term
Linear Equation
Definition
An equation that can be written in the form a1X1 + a2X2 + ... + anXn = b
Term
System of Linear Equations
Definition

A collection of one or more linear equations involving the same variables. A system of linear equations has either:

1) no solution, or

2) Exactly one solution, or

3) Infinitly many solutions.

Term
Consistent
Definition
If a system of linear equations has either one solution or infinitly many solutions
Term
Elementary row operations
Definition

1) (replacement) Replace one row by the sum of itself and a multiple of another

2) (Interchange) Interchange two rows

3) (Scaling) Multiply all entries in a row by a nonzero constant.

Term
Inconsistent
Definition
If a system of linear equations has no solution
Term
The two fundamental questions about a linear system
Definition

1) Is the system consistent (does at least one solution exist)?

2) If a solution does exist, is it unique?

Term
Reduced Echelon form
Definition

1) All nonzero rows are above any rows of all zeros

2) each leading entry of a row is in a column to the right of the leading entry of the row above it.

3) all entries in a column below a leading entry are zeros.

4) The leading entry in each nonzero row is 1.

5) Each leading 1 is the only nonzero entry in its column.

Term
Pivot Position
Definition
A location in matrix A that corresponds to a leading 1 in the reduced echelon form of A. A Pivot column is a column of A that contains a pivot position.
Term
Algebraic Properties of R ^ n
Definition

For all vectors U, V, and W in R ^ n and all scalars C and D:

1) U + V = V + U

2) (U + V) + W = U + (V + W)

3) U + 0 = 0 + U = U

4) U + (-U) = -U + U = 0

5) C(U + V) = CU + CV

6) (C + D)U = CU + DU

7) C(DU) = (CD)U

8) 1U = U

Term
Linear Combination
Definition
A sum of scalar multiples of vectors. The scalars are called the weights.