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A First Course in Linear Algebra, 2017a

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Table of Contents<br />

Table of Contents<br />

iii<br />

Preface 1<br />

1 Systems of Equations 3<br />

1.1 Systems of Equations, Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3<br />

1.2 Systems of Equations, <strong>Algebra</strong>ic Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 7<br />

1.2.1 Elementary Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9<br />

1.2.2 Gaussian Elim<strong>in</strong>ation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14<br />

1.2.3 Uniqueness of the Reduced Row-Echelon Form . . . . . . . . . . . . . . . . . . 25<br />

1.2.4 Rank and Homogeneous Systems . . . . . . . . . . . . . . . . . . . . . . . . . . 28<br />

1.2.5 Balanc<strong>in</strong>g Chemical Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33<br />

1.2.6 Dimensionless Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35<br />

1.2.7 An Application to Resistor Networks . . . . . . . . . . . . . . . . . . . . . . . . 38<br />

2 Matrices 53<br />

2.1 Matrix Arithmetic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53<br />

2.1.1 Addition of Matrices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55<br />

2.1.2 Scalar Multiplication of Matrices . . . . . . . . . . . . . . . . . . . . . . . . . . 57<br />

2.1.3 Multiplication of Matrices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58<br />

2.1.4 The ij th Entry of a Product . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64<br />

2.1.5 Properties of Matrix Multiplication . . . . . . . . . . . . . . . . . . . . . . . . . 67<br />

2.1.6 The Transpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68<br />

2.1.7 The Identity and Inverses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71<br />

2.1.8 F<strong>in</strong>d<strong>in</strong>g the Inverse of a Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73<br />

2.1.9 Elementary Matrices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79<br />

2.1.10 More on Matrix Inverses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87<br />

2.2 LU Factorization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99<br />

2.2.1 F<strong>in</strong>d<strong>in</strong>g An LU Factorization By Inspection . . . . . . . . . . . . . . . . . . . . . 99<br />

2.2.2 LU Factorization, Multiplier Method . . . . . . . . . . . . . . . . . . . . . . . . 100<br />

2.2.3 Solv<strong>in</strong>g Systems us<strong>in</strong>g LU Factorization . . . . . . . . . . . . . . . . . . . . . . . 101<br />

2.2.4 Justification for the Multiplier Method . . . . . . . . . . . . . . . . . . . . . . . . 102<br />

iii

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