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Math Help - this should be really simple (Headbang)

  1. #1
    Newbie scouser's Avatar
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    Angry this should be really simple (Headbang)

    2^y+1 = 3x 5^y
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  2. #2
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    Quote Originally Posted by scouser View Post
    2^y+1 = 3x 5^y
    I think the above means the following:

    . . . . . 2^y\, +\, 1\, =\, (3x)(5^y)

    But what are you supposed to do with this? What were the instructions?

    Thank you!
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  3. #3
    Newbie scouser's Avatar
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    sorry

    sorry i expressed that badly
    ok
    2 to the power of y+1 is equal to 3 times (5 to the power of y)
    Im supposed to find y
    thanks in advance
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  4. #4
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    Quote Originally Posted by scouser View Post
    2 to the power of y+1 is equal to 3 times (5 to the power of y)
    Im supposed to find y
    So you are supposed to solve the equation, which is as follows:

    . . . . . 2^{y+1}\, =\, 3\left(5^y\right)

    A good start for solving this exponential equation would probably be to take the log of either side:

    . . . . . \ln(2^{y+1})\, =\, \ln(3(5^y))

    Apply a log rule to split apart the right-hand side:

    . . . . . \ln(2^{y+1})\, =\, \ln(3)\, +\, \ln(5^y)

    Use the definition of logs to simplify as:

    . . . . . (y\, +\, 1)\ln(2)\, =\, \ln(3)\, +\, (y)\ln(5)

    Then solve this linear equation for "y=".
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  5. #5
    Newbie scouser's Avatar
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    and then

    yeah i had got up to there already.
    then im stuck!
    are you stuck also hahahahaha?
    joking
    please continue explaining
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  6. #6
    Super Member Showcase_22's Avatar
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    ln 5, ln2 and ln 3 are just numbers!

    Solve it for y as such!

    (I can also safely say that Stapel isn't stuck!)

    Read the links that have been posted and post back your attempt.
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  7. #7
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    Quote Originally Posted by scouser View Post
    yeah i had got up to there already.
    then im stuck!
    In future, please show the work you've done.

    In this case, I showed the hard part on the assumption that you'd already studied the easy part. (It's highly unusual to teach how to work with logarithms before having taught how to solve linear equations.) To learn how to do the remaining step, please try here.

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  8. #8
    Newbie scouser's Avatar
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    oh sure, i get it
    thanks
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