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    How would you go about the following question.

    A= [2 -4] AB= 2[0 4] A-1 (inverse) = 1/8 [-2 4]
    [3 -2] [1 4] [-3 2]


    Find what B is

    P.S. sorry for the bad notations

    thanks
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    (Original post by sister_x)
    How would you go about the following question.

    A= [2 -4] AB= 2[0 4] A-1 (inverse) = 1/8 [-2 4]
    [3 -2] [1 4] [-3 2]


    Find what B is

    P.S. sorry for the bad notations

    thanks
    multiply AB by A-1: ABA-1 which = B
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    are you sure?
    I don't get the answer out.
    its question 3b pg 142 of the edexcel FP1 text book, if you have it.
    The answer should be [1 2]
    [1/2 -1]
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    (Original post by dichr0ic)
    ABA-1 = B
    :nope:
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    (Original post by dichr0ic)
    multiply AB by A-1: ABA-1 which = B
    sort of right, with matricies you must pre-multiply, so it'd be A^-1AB and pre-multiply the other side aswell
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    (Original post by blueJ-)
    sort of right, with matricies you must pre-multiply, so it'd be A^-1AB and pre-multiply the other side aswell
    ty

    i thought what i wrote looked a bit weird :o:
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    sorry what do you mean A^-1AB??
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    (Original post by sister_x)
    sorry what do you mean A^-1AB??
    A^-1 is the inverse of A so they cancel
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    so basically I do inverse A multiplied by AB which will equal B?
    I tried that it doesn't work
    its question 3 in the attachment
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    (Original post by sister_x)
    so basically I do inverse A multiplied by AB which will equal B?
    I tried that it doesn't work
    its question 3 in the attachment
    The inverse of A is not needed in part b, I think the question was a little ambigious so no one bothered trying to work it out and just said what you could try. Anyway

    (2 -4) (a b) = (0 8)
    (3 -2) (c d) = (2 8)

    That's what the question tells you, now you've got to find a b c d which gives you matrix B.
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    thanks I managed to get the answer out LOL wasn't too hard in the end
 
 
 
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