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Homework Help: Using cramer's Rule to solve for x2, i'm confused on this example!

  1. Oct 23, 2005 #1
    I scanned the page out of the book, alittle bit is kinda burly but i'm confused on how they got A_2(B), where we are thinking of the system in matrix form AX = B. One verfies that detA = -127 and det[A_2(B)] = 313, so
    x2 = det[A_2(B)]/det(A) = 313/-127 = -313/127;

    How did they get B? and det[A_2(B)] here is the picture:
    http://img416.imageshack.us/img416/9428/lastscan5eu.jpg [Broken]
    thanks.
     
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Oct 23, 2005 #2
    nevermind i found the pattern, all they do is replace the 2nd column with the values after the =.
     
  4. Oct 23, 2005 #3

    TD

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    Homework Helper

    Correct, to find the 'n-th' unknown with Cramer's rule, you have to replace the n-th column by the column of the constants.
     
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