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Linear algebra, find values

  1. Feb 1, 2012 #1
    Find the value of x when the matrix equals 3:

    |x-2 3|
    |x x+1|

    so I find the determinant:
    (x-2)(x+1)-(x)(3)
    x^2-4x-2

    How do I find which values are giving 3 from here?
     
  2. jcsd
  3. Feb 1, 2012 #2

    vela

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    You mean when the determinant of the matrix equals 3. The matrix doesn't equal 3.

    You found
    $$\begin{vmatrix} x-2 & 3 \\ x & x+1 \end{vmatrix} = x^2-4x-2$$ so set that expression equal to 3 and solve for x.
     
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