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Math Help - quadratic?

  1. #1
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    quadratic?

    two questons, are they both quadratic? if anyone could get me started much appreciated.

    (a) 3{^2{^x}}+ 8 . 3{^x}-9=0 (multiply 8 x 3x)

    (b) e{^2{^x}}+ 8e{^x}=3^2
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  2. #2
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    Quote Originally Posted by decoy808 View Post
    two questons, are they both quadratic? if anyone could get me started much appreciated.

    (a) 3{^2{^x}}+ 8 . 3{^x}-9=0 (multiply 8 x 3x)

    (b) e{^2{^x}}+ 8e{^x}=3^2
    hi
    you can put 3^x=X and see what happens.
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  3. #3
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    b)

    define e^x = u then the equation is equivalent to  u^2+8u-9=0

    Factoring

    (u+9)(u-1)=0

    solutions u=1 and u=-9

    As the exponential negative values does not yield, the solution is

    u=1=e^x \rightarrow x=0
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