math136

# math136 - ASSIGNMENT 1 Solutions In questions 1 and 2 find...

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Unformatted text preview: ASSIGNMENT 1 Solutions In questions 1 and 2, find all real values of a for which the system has: (i) exactly one solution; (ii) no solutions; and (iii) infinitely many solutions. 1. [2 marks]- x 1 + 3 x 2 + 2 x 3 =- 1 2 x 1- 9 x 2- 4 x 3 = 12 x 1 + 3 x 2 + ax 3 = a 2- 23 The augmented matrix of the system, - 1 3 2- 1 2- 9- 4 12 1 3 a a 2- 23 , reduces to the matrix - 1 3 2- 1- 3 10 a + 2 ( a + 2) ( a- 2) , whence the system has (i) exactly one solution if a 6 =- 2 ; (ii) no solutions never; and (iii) infinitely many solutions if a =- 2 . 2. [4 marks] ax 2 1 + x 2 2 = a 2 ( a 2- 2 a- 2 ) x 2 1- 3 x 2 2 =- a 4- 2 a Let X 1 = x 2 1 and X 2 = x 2 2 , and consider the system X 2 + aX 1 = a 2- 3 X 2 + ( a 2- 2 a- 2 ) X 1 =- a 4- 2 a. The augmented matrix reduces to the matrix M = " 1 a a 2 ( a + 2) ( a- 1)- a ( a + 2) ( a- 1) 2 # . Suppose a = 0 . Then M reduces further to the matrix 1 1 — hence x 2 1 = x 2 2 = 0 ; that is, x 1 = x 2 = 0 . Suppose a 6 = 0 . If a =- 2 or a = 1 , M reduces to 1- 2 4 or 1 1 1 , respectively. In the first case, we haverespectively....
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## This note was uploaded on 04/07/2010 for the course MATH 136 taught by Professor All during the Fall '08 term at Waterloo.

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math136 - ASSIGNMENT 1 Solutions In questions 1 and 2 find...

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