4 Vecttors and Matrices 　 4.1 INTRODUCTION 4.2 VECTORS 4.3 MATRICES 4.4 MATRICES ADDITION AND SCALAR MULTIPLICATION 4.5 SUMMATION SYMBOL 4.6 MATRIX MULTIPLICATION 4.7 TRANSPOSE 4.8 SQUARE MATRICES 4.9 INVERTIBLE MATRICES 4.10 DETERMINANTS 4.11 INVERTIBLE MATRICES AND DETERMINANTS