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Math Help - More logs!

  1. #1
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    More logs!

    Can anyone help??

    Solve log5(x^2 + x + 4) = 2


    and

    Solve log4 (x^2 +9) - log4(x+3) = 3

    Thanks everyone!
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  2. #2
    A riddle wrapped in an enigma
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    Quote Originally Posted by rtwilton View Post
    Can anyone help??

    Solve log5(x^2 + x + 4) = 2
    \log_5(x^2+x+4)=2

    x^2+x+4=5^2

    Can you finish?


    Quote Originally Posted by rtwilton View Post
    Solve log4 (x^2 +9) - log4(x+3) = 3

    Thanks everyone!

    \log_4(x^2+9)-\log_4(x+3)=3

    \log_4\frac{x^2+9}{x+3}=3

    \frac{x^2+9}{x+3}=4^3

    Can you finish?
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  3. #3
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    finish...

    I got as far as you did on both, but then I got stuck. I dunno sometimes it's the easy stuff that confuses me...
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  4. #4
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    Quote Originally Posted by rtwilton View Post
    I got as far as you did on both, but then I got stuck. I dunno sometimes it's the easy stuff that confuses me...

    x^2+x+4=25

    x^2+x-21=0

    This won't factor, so use the quadratic formula to find x.
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  5. #5
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    Ahh the quadratic formula, of course!
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  6. #6
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    So I came up with negative 1/2 plus or minus the square root of 26 divided by 2. Dont know how to write that any better, and can it be simplified any further??
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  7. #7
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    Quote Originally Posted by rtwilton View Post
    So I came up with negative 1/2 plus or minus the square root of 26 divided by 2. Dont know how to write that any better, and can it be simplified any further??
    I'm not sure how you managed to come up with that answer.

    x^2+x-21=0

    x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}

    x=\frac{-1\pm\sqrt{1^2-4(1)(-21)}}{2(1)}

    x=\frac{-1\pm\sqrt{85}}{2}
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  8. #8
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    Well I had almost the same answer as you, see I added the 21 and 4 instead of multiplying!!
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