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Homework Help: Pre Calc, how to you solve an equation if it says a≠0? please help!

  1. Sep 11, 2010 #1
    it says "use the inverses found in Problems 29-38 to solve each system of equations"(not sure what it means by that)
    pg742,#47)
    2x+y= -3
    ax+ay=-a
    a≠0 <----a≠0 was already in the book next to the equation
    the book says the answer is x=-2,y=1
    -what i have so far-
    [2 1] [-3] --> (2 x a)-(a x 1) = 1a
    [a a]=[-a]
    [a -1]
    A^-1= 1/det(A) x [-a 2]

    [a -1] [1 -1/a]
    A^-1= 1/1a x [-a 2] = [-1 2/a] <---inverse

    [x] [1 -1/a] [-3]
    [y] = [-1 2/a] [-a]


    50) bx+3y= 14
    bx+2y=10
    b≠0 <------b≠0 was already in the book next to the equation

    My math book is called "Precalculus seventh edition Sullivan", its a dark green/blue color(just in case you might have it). on pg 742 it says "show that each matrix has no inverse"
     
  2. jcsd
  3. Sep 11, 2010 #2

    Mark44

    Staff: Mentor

    Everything looks fine, so far. What do you get for x and y when you do the matrix multiplication on the right?
    Do the same thing you did in the previous problem to find the solution for this problem.
     
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