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Math121 Discussion - 4th week answers

# Math121 Discussion - 4th week answers - 3(a(4 A-3 D B =...

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MATH 121 DISCUSSION WEEK 4 SOLUTIONS 1) When we transform our augmented matrix using Gauss-Jordan, we get a row 0 = 2, which is impossible. Therefore, the system has no solutions. 1 2 - 4 4 0 1 6 - 3 0 0 0 2 2) (a) 1 3 5 1 4 7 - 2 - 4 - 6 x y z = 2 6 4 (b) When we transform our augmented matrix, we get a row of all 0’s. This shows that the system has an inﬁnite number of solutions. 1 3 5 2 0 1 2 4 0 0 0 0 (c) ( x,y,z ) = ( z - 10 , 4 - 2 z,z ) where z is any real number
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Unformatted text preview: 3) (a) (4 A-3 D ) B = ±-182 114 ² (b) A ( CD ) + 5 A = ± 715 483-91 253 201-145 ² (c) A and C are not square matrices. (d) ( 1 2 )(7)-(-7 4 )(-2) = 7 2-7 2 = 0. 1 is undeﬁned, so E-1 does not exist. (e) ± 1 2-7 4-2 7 ²± x y ² = ±-2 18 ² ⇐⇒ ³ 1 2 x-7 4 y =-2-2 x + 7 y = 18 4) (a) ( x,y ) = ( 3 11 ,-21 11 ) (b) ( x,y ) = ( 43 3 , 29) 1...
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