1. The problem statement, all variables and given/known data Let ej denote the jth unit column that contains a 1 in the jth position and zeros everywhere else. For a general matrix An×n, describe the following products. (a) Aej (c) eTiAej? 2. Relevant equations Rows and Columns of a Product Suppose that A = [aij] is m × p and B = [bij] is p × n. • [AB]i∗ = Ai∗B [( ith row of AB)=( ith row of A) ×B]. (3.5.4) • [AB]∗j = AB∗j [ (jth col of AB)=A× ( jth col of B)]. (3.5.5) • [AB]i∗ = ai1B1∗ + ai2B2∗ + · · · +aipBp∗ =Ʃ aikBk∗. (3.5.6) • [AB]∗j = A∗1b1j + A∗2b2j + · · · + A∗pbpj=Ʃ A∗kbkj (3.5.7) These last two equations show that rows of AB are combinations of rows of B, while columns of AB are combinations of columns of A. 3. The attempt at a solution For parts a and c im not even sure what they are even asking for. When its saying ej is a unit column does that mean like this (1 0 0...0) as an example? For part A wouldn't the solution of Aej just just be a linear combination a column of A and the entries of ej as scalars?