ProblemSet3 Solutions

ProblemSet3 Solutions - Department of Economics Ryerson...

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Department of Economics Ryerson University ECN230-Mathematics For Economics Problem Set #3 - Solutions EXERCISE 4.2 Problem 2: (a) Number of columns of A =Numberofrowsof B =2 : AB is de f ned. AB = 28 30 51 20 38 ¸ = 4+24 0+64 6+0 0+0 10 + 3 0 + 8 = 28 64 60 13 8 . Number of columns of B 6 A =3: BA is not de f ned, because the two matrices are not conformable. (b) Both matrix products are de f ned, but BC 6 = CB . In particular, = ¸ 72 63 ¸ = 14 4 69 30 ¸ and = ¸ ¸ = 20 16 21 24 ¸ . Problem 3 Number of columns of B =Numbero frowso f A =3 : is de f ned. AB = 0 1 5 3 10 1 1 5 7 10 0 2 5 1 10 3 12 10 3 40 2 = 100 010 001 . 1
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Thus, in this particular case, AB = BA . Problem 4: (a) 020 304 230 80 01 35 = 02 36 20 16 3 (3 × 3) (3 × 2) (3 × 2) (b) 65 1 10 4 ¸ 4 1 52 = 49 3 43 ¸ (2 × 3) (3 × 2) (2 × 2) (c) 35 0 42 7 ¸ x y z = 3 x +5 y 4 x +2 y 7 z ¸ (2 × 3) (3 × 1) (2 × 1) (d) £
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This homework help was uploaded on 04/18/2008 for the course ECONOMICS ECN 230 taught by Professor Angrydis during the Winter '08 term at Ryerson.

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ProblemSet3 Solutions - Department of Economics Ryerson...

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