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How would you do this maths question?

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    The variables x and y and the constants a and b are real and positive. The variables x and y are related.

    A graph of log y against log x is drawn.

    For which one of the following relationships will this graph be a straight line?

    1) y^6=a^x
    2) y=ab^x
    3) y^2=a + x^b
    4) y=ax^b
    5) y^x=a^b

    Thanks a lot
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    Make log(y) the subject by taking the log of both sides.

    So for a it would be 6\log(y)=x\log(a) and this is not of the form \log(y)=m\log(x)+c so the answer is not a.

    Do this for the rest and see which are of the form \log(y)=m\log(x)+c
 
 
 
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