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Question
If A = `[(3, 2),(7, 4)], B = [(0, 5),(2, 3)]`, find AB + ВА.
Sum
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Solution
AB = `[(3, 2),(7, 4)] [(0, 5),(2, 3)]`
= `[(3 xx 0 + 2 xx 2, 3 xx 5 + 2 xx 3),(7 xx 0 + 4 xx 2, 7 xx 5 + 4 xx 3)]`
= `[(0 + 4, 15 + 6),(0 + 8, 35 + 12)]`
= `[(4, 21),(8, 47)]`
BA = `[(0, 5),(2, 3)] [(3, 2),(7, 4)]`
= `[(0 xx 3 + 5 xx 7, 0 xx 2 + 5 xx 4),(2 xx 3 + 3 xx 7, 2 xx 2 + 3 xx 4)]`
= `[(0 + 35, 0 + 20),(6 + 21, 4 + 12)]`
= `[(35, 20),(27, 16)]`
AB + BA = `[(4, 21),(8, 47)] + [(35, 20),(27, 16)]`
= `[(4 + 35, 21 + 20),(8 + 27, 47 + 16)]`
= `[(39, 41),(35, 63)]`
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