# week07 - Math 43, Fall 2007 B. Dodson Week 7: Graded...

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Math 43, Fall 2007 B. Dodson Week 7: Graded Homework 7: 3.1 - 14; 3.2 - 24; 3.3 - 2. due Mon. Oct. 22 Suggested Homework 7: graded Homework plus 3.1 - 3, 4, 5, 15, 23, 35; 3.2 - 1, 2, 23; 3.3 - 3, 11, 35 due Wed. Oct. 24. Seventh week. Matrix Arithmetic; Algebra; Inverses If A and B are both m -by- n -matricies, with A = [ a i,j ] and B = [ b i,j ] the matrix sum C = A + B is the matrix C = [ c i,j ] with i, j -th entry c i,j = a i,j + b i,j . We also have scalar multiplication rA, which has i, j -th entry ra i,j . For matrix multiplication, multiplying two matricies, we start with row-matrix × column-matrix by [ r 1 , r 2 , . . . , r n ] × c 1 c 2 . . . c n = r 1 c 1 + r 2 c 2 + ··· + r n c n . For example [2 , - 1] 3 2 - 1 = . . . and [2 , - 1 , 5] 3 2 - 1 = . . . Finally, if A has rows ± R 1 . . . ± R s and B has columns B = [ ± C 1 , . . . , ± C u ] we set AB = A [ ± C 1 , . . . , ± C u ] = [ A ± C 1 , . . . , A ± C u ] which is the matrix with entries ± R i ± C j , .

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## This note was uploaded on 02/29/2008 for the course MATH 43 taught by Professor Dodson during the Spring '08 term at Lehigh University .

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week07 - Math 43, Fall 2007 B. Dodson Week 7: Graded...

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